OpenLP 2.4.6

Fix a bug where the author type upgrade was being ignore because it was looking at the wrong table
Fix a bug where the songs_songbooks table was not being created because the if expression was the wrong way round
Change the songs_songbooks migration SQL slightly to take into account a bug that has (hopefully) been fixed
Sometimes the timer goes off as OpenLP is shutting down, and the application has already been deleted (reported via support system)
Fix opening the data folder (KDE thought the old way was an SMB share)
Fix a problem with the new QMediaPlayer not controlling the playlist anymore
Add importing of author types to the OpenLP 2 song importer
Fix a problem with loading Qt's translation files, bug #1676163
Disable the controls in the shortcut dialog unless a shortcut is actually selected