STA Operation and additional Unit Tests

Implemented the STA operation. Added additional unit tests for STX and
STY's different addressing modes. Fixed a bug with the  Zero Page Y
addressing mode.
Did some housekeeping.
TAX, TAY, TXA, TYA Operations implemented

Implemented the remaining non-stack transfer operations.
Stubbed out remaining Stack operations

TSX and TXS operations stubbed
StackPointer Now Points to correct place in memory

There was some confusion on my part when comparing the 6502 and 6507,
but thats been sorted out.