Save page class changes (such as addition of bloom-trilingual)

The relevant code for adding the bloom-trilingual (et al) class is in TranslationGroupManager.UpdateContentLanguageClasses.  However, even though the temp page was always getting this added, the real (stored) page was not getting it until a series of other steps were followed (such as leaving the book, returning the page, leaving the page).

So technically, this line was asserting true before my change.  The only line which wasn't was 1286.  I could remove these two asserts if that is better.