Prevent overwriting of portable config on update

* Move portable configuration files into a config subfolder from the executable. This prevents overwriting the stored config when the application is updated in-place.
* Use .portable file to signal a portable app
* Fix #4751

release-tool

@@ -987,13 +987,15 @@ build() {
             cpack -G "${CPACK_GENERATORS};${build_generators}"
 
             # Inject the portable config into the zip build and rename
+            touch .portable
             for filename in ${APP_NAME}-*.zip; do
                 logInfo "Creating portable zip file"
                 local folder=$(echo ${filename} | sed -r 's/(.*)\.zip/\1/')
                 python -c 'import zipfile,sys ; zipfile.ZipFile(sys.argv[1],"a").write(sys.argv[2],sys.argv[3])' \
-                    ${filename} ${SRC_DIR}/share/keepassxc.ini ${folder}/keepassxc.ini
+                    ${filename} .portable ${folder}/.portable
                 mv ${filename} ${folder}-portable.zip
             done
+            rm .portable
 
             mv "${APP_NAME}-"*.* ../
         else