Adds renderbuffer, texture, fbo. Adds get_id() functions.

The renderbuffer and texture wrapper classes are really straightforward and can be pulled right away (I guess).

I needed ```get_id()``` functions on those classes to be able to work with OpenCL. I can image such functionality is also useful when using certain OpenGL extensions (or even functions we do not wrap already).

The ```bare_fbo``` wrapper is also quite easy and lacks (just like ```vao```) the ability to attach temporary textures or renderbuffers. The ```fbo``` on the other hand can attach those (and stores them himself). Maybe such an approach is also possible with vao's?
I'd rather see that after construction the object is valid and usable. This means a constructor that gets more parameters to automatically call storage(), because what's a renderbuffer without storage?

I know this isn't done in moggle now, but continuing a bad trend isn't a good thing, though it is consistent.