[Rewrite] Don't try to resolve every assembly

We only need to resolve mscorlib. This fixes issues when rewriting the
iOS build.
[iOS] Initialize the correct IPlatformFactory
[iOS] Implement extension loading
[Graphics] Disable validity checks on iOS
[iOS] Removed unused EGL platform

iOS uses EAGL instead.
[iOS] Added ES11 sample
[Android] Load ES entry points
Removed SDL2 projects from workspace

The SDL2 projects are completely experimental and should not normally
be used.