Change default file locations (#35)

* Change default files location as described in #27

* config: Change default config file name

directories.go

@@ -0,0 +1,39 @@
+package maddy
+
+import (
+	"os"
+)
+
+var (
+	defaultConfigDirectory  = "/etc/maddy"
+	defaultStateDirectory   = "/var/lib/maddy"
+	defaultLibexecDirectory = "/usr/libexec/maddy"
+)
+
+func ConfigDirectory() string {
+	return defaultConfigDirectory
+}
+
+func StateDirectory(globals map[string]interface{}) string {
+	if dir := os.Getenv("MADDYSTATE"); dir != "" {
+		return dir
+	}
+
+	if val, ok := globals["statedir"]; ok {
+		return val.(string)
+	}
+
+	return defaultStateDirectory
+}
+
+func LibexecDirectory(globals map[string]interface{}) string {
+	if dir := os.Getenv("MADDYLIBEXEC"); dir != "" {
+		return dir
+	}
+
+	if val, ok := globals["libexecdir"]; ok {
+		return val.(string)
+	}
+
+	return defaultLibexecDirectory
+}