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

testing/project_setup/custom_command/1_setup.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+# get absolute path to parent directory of script
+MY_PATH=`dirname "$0"`
+if [[ "${MY_PATH}" != *\\* ]]
+then
+	cd $MY_PATH
+	MY_PATH=`pwd`
+fi
+MY_PATH="${MY_PATH//\\//}"
+
+SRC_PATH=$MY_PATH/data
+WORKING_COPY_PATH=$MY_PATH/working_copy
+
+mkdir -p $WORKING_COPY_PATH
+
+cp -a $SRC_PATH/. $WORKING_COPY_PATH
+
+echo "Setup Complete"