fix for web browser and other app resolution problems

[Albert Cahalan]

Several hacks have been tried. They all break web sites, with no way
for the user to deal with the result. The latest hack kills
performance and degrades image quality.

There are other apps to deal with as well, beyond the web browser.

Just as the user can select the screen rotation and color/mono mode,
the user should be able to select a screen resolution. The useful
resolutions are 1200x900, 600x450, and 400x300. Simple integer scaling
can cover all of these.

Sugar should remember these settings (resolution, color/mono,
rotation, backlight, swizzle, gamma, etc.) for each running app, so
that switching between apps will switch the settings. Sugar should
also let apps supply a list of incompatible modes and flags to
indicate if the app can tolerate run-time switching of the various
settings.