Create docs directory and QUICKSTART.md instructions; editorial pass … (#1227)

Create docs directory and QUICKSTART.md instructions; editorial pass on README and INSTALL

INSTALL.md

@@ -1,11 +1,13 @@
-Install KeePassXC
+Build and Install KeePassXC
 =================
 
-This document will guide you across the steps to install KeePassXC.
-You can visit the online version of this document at the following link
+This document will guide you through the steps to build and install KeePassXC from source.
+You can visit the online version of this document at the following link:
 
 https://github.com/keepassxreboot/keepassx/wiki/Install-Instruction-from-Source
 
+The [KeePassXC QuickStart](./docs/QUICKSTART.md) gets you started using KeePassXC on your 
+Windows, Mac, or Linux computer using the pre-built binaries.
 
 Build Dependencies
 ==================
@@ -28,10 +30,9 @@ The following libraries are required:
 Prepare the Building Environment
 ================================
 
-* Building Environment on Linux    ==> https://github.com/keepassxreboot/keepassxc/wiki/Set-up-Build-Environment-on-Linux
-* Building Environment on Windows  ==> https://github.com/keepassxreboot/keepassxc/wiki/Set-up-Build-Environment-on-Windows
-* Building Environment on MacOS    ==> https://github.com/keepassxreboot/keepassxc/wiki/Set-up-Build-Environment-on-OS-X
-
+* [Building Environment on Linux](https://github.com/keepassxreboot/keepassxc/wiki/Set-up-Build-Environment-on-Linux)
+* [Building Environment on Windows](https://github.com/keepassxreboot/keepassxc/wiki/Set-up-Build-Environment-on-Windows)
+* [Building Environment on MacOS](https://github.com/keepassxreboot/keepassxc/wiki/Set-up-Build-Environment-on-OS-X)
 
 Build Steps
 ===========
@@ -39,32 +40,68 @@ Build Steps
 To compile from source, open a **Terminal (on Linux/MacOS)** or a **MSYS2-MinGW shell (on Windows)**<br/>
 **Note:** on Windows make sure you are using a **MINGW shell** by checking the label before the current path
 
-Navigate to the path you have downloaded KeePassXC and type these commands:
+First, download the KeePassXC [source tarball](https://keepassxc.org/download#source) 
+or check out the latest version from our [Git repository](https://github.com/keepassxreboot/keepassxc).
+
+To clone the project from Git, `cd` to a suitable location and run
+
+```bash
+git clone https://github.com/keepassxreboot/keepassxc.git
+```
+
+This will clone the entire contents of the repository and check out the current `develop` branch.
+
+To update the project from within the project's folder, you can run the following command:
+
+```bash
+git pull
+```
+
+Navigate to the directory where you have downloaded KeePassXC and type these commands:
 
 ```
+cd directory-where-sources-live
 mkdir build
 cd build
-cmake -DWITH_TESTS=OFF
+cmake -DWITH_TESTS=OFF ...and other options - see below...
 make
 ```
+These steps place the compiled KeePassXC binary inside the `./build/src/` directory. 
+(Note the cmake notes/options below.)
 
-**Note:** If you are on MacOS you must add this parameter to **Cmake**, with the Qt version you have installed<br/> `-DCMAKE_PREFIX_PATH=/usr/local/Cellar/qt5/5.6.2/lib/cmake/`
+**Cmake Notes:** 
 
-You will have the compiled KeePassXC binary inside the `./build/src/` directory.
+* Common cmake parameters
 
-Common cmake parameters
-```
--DCMAKE_INSTALL_PREFIX=/usr/local
--DCMAKE_VERBOSE_MAKEFILE=ON
--DCMAKE_BUILD_TYPE=<RelWithDebInfo/Debug/Release>
--DWITH_GUI_TESTS=ON
-```
+	```
+	-DCMAKE_INSTALL_PREFIX=/usr/local
+	-DCMAKE_VERBOSE_MAKEFILE=ON
+	-DCMAKE_BUILD_TYPE=<RelWithDebInfo/Debug/Release>
+	-DWITH_GUI_TESTS=ON
+	```
 
+* cmake accepts the following options:
+
+	```
+	  -DWITH_XC_AUTOTYPE=[ON|OFF] Enable/Disable Auto-Type (default: ON)
+	  -DWITH_XC_HTTP=[ON|OFF] Enable/Disable KeePassHTTP and custom icon downloads (default: OFF)
+	  -DWITH_XC_YUBIKEY=[ON|OFF] Enable/Disable YubiKey HMAC-SHA1 authentication support (default: OFF)
+	
+	  -DWITH_TESTS=[ON|OFF] Enable/Disable building of unit tests (default: ON)
+	  -DWITH_GUI_TESTS=[ON|OFF] Enable/Disable building of GUI tests (default: OFF)
+	  -DWITH_DEV_BUILD=[ON|OFF] Enable/Disable deprecated method warnings (default: OFF)
+	  -DWITH_ASAN=[ON|OFF] Enable/Disable address sanitizer checks (Linux / macOS only) (default: OFF)
+	  -DWITH_COVERAGE=[ON|OFF] Enable/Disable coverage tests (GCC only) (default: OFF)
+	```
+
+* If you are on MacOS you must add this parameter to **Cmake**, with the Qt version you have installed<br/> `-DCMAKE_PREFIX_PATH=/usr/local/Cellar/qt5/5.6.2/lib/cmake/`
+
+:exclamation: When building with ASan support on macOS, you need to use `export ASAN_OPTIONS=detect_leaks=0` before running the tests (no LSan support in macOS).
 
 Installation
 ============
 
-To install this binary execute the following:
+After you have successfully built KeePassXC, install the binary by executing the following:
 
 ```bash
 sudo make install