Debugger additions

Added Expression Parser, fixed some issues.

**Expression Parser:**
Supports `+`, `-`, `*`, `/` (integer math only), `%`, `(`, `)`, `{`, and `}`. All these, except  `{` and `}` work as presumed. You can also use numbers, and registers. The `{` and `}` are dereference operators, dereferencing the value contained within. To test this, another command is made, called `print_expression`, or simply `expression` in the debugger.