MechModel fixes...

- Only one of the MechModel::MechModelNode::{data,constData} pointers
  are used per object instance. Therefore put them in an union.
- Fix MechModel::removeRows(). This closes issue #14
Optimize getAllDirectionPairs().
Standardize on QVector as the main container for various consts.
Simplify BTech::Matrix
Adnotate magic consts and tables with references to rulebook.
More rulebook adnotations and minor style corrections.
Divided Bases into Bases and Models

-Added separate directories Bases and Models for bases and models.
-Base class and Model class are no longer in the same .h/.cpp file
This closes issue #12.