Implement scaling modes manually

[AllyTally]

Changes:

For future PRs, it'll be very nice to have full control over how VVVVVV gets drawn to the window. This means we can use the entire window size for things like touch input, drawing borders, or anything we want.

Legal Stuff:

By submitting this pull request, I confirm that...

• [x] My changes may be used in a future commercial release of VVVVVV
• [x] I will be credited in a CONTRIBUTORS file and the "GitHub Friends" section of the credits for all of said releases, but will NOT be compensated for these changes unless there is a prior written agreement

[InfoTeddy]

Conflicts need to be resolved.