Split BitmapHandler into two classes.

BitmapHandler has a lot of generic-ish functionality that could
be re-usable by extension classes (Such as how it organizes
$scalerParams array, or various image magick escaping methods).
However it's combined with a lot of very format specific things,
such as the shell-out call to image magick.

Try to separate out the more generic stuff into
TransformationalImageHandler. In order to do this, I also made
canRotate, autoRotateEnabled, and getScalerType non-static. No
extensions in our repo appeared to be using these methods, and they
don't really make sense to be static (imo).

In particular, I think code duplication can be reduced in
PagedTiffHandler by extending this new class. See comments
on I1b9a77a4a56eeb65.

Change-Id: Id3a8b25a598942572cb5791a95e86054d7784961
Merge "Split BitmapHandler into two classes."