Added WrapperTypes.ConvenienceArrayType

These are convenience parameters for function receiving a size and an
array parameter, like DeleteTextures(int n, int[] ids). The generator
will now add overloads taking a single parameter, such as
DeleteTexture(int id).
Restrict convenience overloads

Only Get*, Gen*, Delete* and New* functions get convenience overloads.
This avoids issues with functions such as Rect() that have similar
signatures but cannot use such overloads.

This restriction will be relaxed in the future.
Updated convenience overloads