Initial commit to fix MML issue MegaMek#1182.
Adds more fields to bay representation in strings and objects;
normalizes string representations so all bays use the same fields
in the same ways - no more bay #, _or_ infantry type, _or_ facing
in one field.

Added a test file for BLKDropshipFile.java that reads a BLK-file
string in and confirms new BattleArmor bay behavior.

I ended up not needing Mockito after all.

Add some extra exception handling, fix string equality check,
make bit-wise operation safer.

It appears that we have been writing empty <transporters> blocks
into every vehicle for the past 6 or so years.  These blocks should
not exist in, e.g., combat vehicles, but apparently went unnoticed
due to loose handling of the relevant block when empty.

This change adds a new test prior to processing these empty blocks
on file load, a function to support this test, and a conditional
around writing the <transporters> block to prevent writing empty
blocks in every .BLK file.

New function "containsData" encompasses this call already.