logic: Added SourceGroupCustomCommand to use with SourcetrailDB binaries

* Added new Source Group type SourceGroupCustomCommand to UI and ProjectSettings
* The Source Group executes a specified command on every source file
* The variables $SOURCE_PATH, $PROJECT_PATH, $DB_PATH, $STORAGE_VERSION can be passed
* The commands are executed after all other source groups finished indexing
* The command is executed with working directory set to project directory
* Errors during command execution are shown as status update and in the Status View
* SourceGroupCustomCommand cannot be partially cleared, when one file needs clearing the project must be fully re-indexed

src/lib/settings/SourceGroupSettingsJavaSonargraph.cpp

@@ -44,8 +44,3 @@ bool SourceGroupSettingsJavaSonargraph::equals(std::shared_ptr<SourceGroupSettin
 		SourceGroupSettingsWithSonargraphProjectPath::equals(otherJavaSonargraph)
 	);
 }
-
-const ProjectSettings* SourceGroupSettingsJavaSonargraph::getProjectSettings() const
-{
-	return m_projectSettings;
-}