[WIP] - Code Printing refactor, matrix support

** Edit **
This started out as just adding support for `Matrix` in codeprinting/codegen, but turned into a fairly substantial refactor of the existing codebase. I have updated this to reflect that. The TODO list is a trimmed down version of the original TODO, `autowrap` support should come in a later PR, this only has to do with printing now.

See my mammoth sized comment below for what's inside this PR now
** end edit **

TODO:
- [x] Support for matrix output in ccode and CCodeGen
- [x] Support for matrix output in fcode and FCodeGen
- [x] Support for `MatrixSymbol` input in ccode and CCodeGen
- [x] Support for `MatrixSymbol` input in fcode and FCodeGen
- [x] Tests
You're right about c and fortran, but the generator exrpression is evaluated right to left, so it will traverse the columns inside the rows (do all of row 1, then all of row 2, ...).