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_gui/utility/utilityApp.cpp

@@ -96,7 +96,8 @@ int utility::executeProcessAndGetExitCode(
 	const std::wstring& commandPath,
 	const std::vector<std::wstring>& commandArguments,
 	const FilePath& workingDirectory,
-	const int timeout
+	const int timeout,
+	std::wstring* processOutput
 ){
 	QProcess process;
 
@@ -124,7 +125,14 @@ int utility::executeProcessAndGetExitCode(
 	}
 
 	int exitCode = process.exitCode();
+
+	if (processOutput != nullptr)
+	{
+		*processOutput = utility::trim(QString(process.readAll()).toStdWString());
+	}
+
 	process.close();
+
 	return exitCode;
 }