Add missing constructor to VertexAttribAttribute
Update ImageUniform methods to current texture object structure
Add all remaining OpenGL texture types

Update corresonding methods with lots of overloads on ImageUniform and FrameBuffer
Add assertion that a texture actually contains a given mipmap level before accessing it
Unify FrameBuffer.Attach methods
Remove old files

How did they not get deleted?
Simplify texture constructors with respect to mipmap levels
Simplify texture constructors with respect to the appropriate TextureTarget
Add generic TextureUniform to allowed type-safe texture binding
Refactor texture creation and loading

Move load methods to TextureExtensions.
Change the default number of mipmap levels when creating new textures to be the maximum allowed number instead of one (no mipmaps).