Move unrelated code from projectmodel.{cpp,h}
Summary:
projectmodel: Extract class UpdateStatsJob into separate source files
projectmodel: Move FileMetaData extraction function into class FileMetaData
Test Plan: it compiles
Reviewers: sdepiets
Reviewed By: sdepiets
Subscribers: Localization
Differential Revision: https://phabricator.kde.org/D21843