Added upgrade routine, and fixed spelling of "persistance".

This commit adds an upgrade routine to move all the preference files into one location, the new prefs/ folder. Additionally, compiler warnings are shown by default in the logger-preferences.ini. The old loggerPreferences.txt is being deleted, since the new default is being changed, and few people were probably using that anyways, but compiler warnings are good to show by default. Additionally, all non-functional instances of "persistance" have been renamed to the correct spelling of "persistence". There are a few places where the incorrect spelling is being left, because they would actually require upgrade routines to fix.