Added a console to wxApplication along with some basic commands

[arkhaix]

The console is implemented as a new wxFrame with two wxTextCtrl elements. This still needs a few more features before I'll be happy with it, but this is a good foundation.

Future todos:

• Window resizing (text controls don't expand yet)
• Command aliases ('ss' = 'savestate')
• Autocompletion (prefix tree, tab interception)
• Debugging commands (instruction stepping, breakpoints, memory viewing)
• Audio commands (needs interface changes)
• Recording/Playback commands (movies and macros)

[arkhaix]

refs #5