Restructuring Math classes

The Math.body file which contains the MathRender class was split in the following way:
- Math.base contains the base class with the database related stuff and provides an abstract interface
- Math.source and Math.MathJax handle the plain tex string output. There are two classes since they
  will differntiate in the future I think.
- Math.texvc contains the "old" implementation of png generation with all the file handling related stuff
- Other implementation of math renderer can be added in the same style.
- Cleanup to better follow coding conventions.
- Changed LockManager to 'fsLockManager'

The first attempt restructure the class layout and introduce LaTeXML at the same
time was dropped. Instead this was split up into two phases.
This commit only deals about the restructuring of the math module design.

Change-Id: I9b1d68c4faa8d177d8d0088fa1a5879caed4f1fe