ios es2 cleanup

- fixes shader errors in issue #2233 with the use of ofGLReadyCallback()
- added enableRendererES20() and enableRendererES11() methods to
ofAppiPhoneWindow
- updated code that references ofGLProgrammableRenderer, mainly now
using ofIsGLProgrammableRenderer() which was recently introduced.
- cleaned up ofAppiPhoneWindow (formatting + removed old code)
Merge branch 'develop' of https://github.com/openframeworks/openFrameworks into ios-es2-cleanup
added ofReloadGLResources()
renamed ES11 to ES1 and ES20 to ES2 - for simplicity
Merge pull request #2248 from julapy/ios-es2-cleanup

ok good to merge.