OMML: Reader unqualify TeXMath types

We don't have to worry about collisions anymore.
First stab at intepreting string types.
OMML: improve grouping.
Move Exp-processing functions to Shared.

These aren't specific to MathML.
Fix one more String-processing part.
Add fixTree to OMML.
Fix Groupings in Delims.
Fix TextType error.
Merge pull request #60 from jkr/cleanup

OMML fixes.