Refactoring of AbstractConversationViewFragment.

In order to support EML viewing, we need a bunch of
the overhead provided by AbstractConversationViewFragment
without actually inheriting from it. Additionally, most of
the code was inner classes that had no business being such.
These are now moved into their own classes.

Change-Id: I80769d2606b52c41dc116a6bdee17c00adc66a5a
12 files changed