Adding better instanced rendering support and buffer textures

[Gaalve]

This PR adds the following functionalities:

• Instanced Rendering
  • fixed: you can now specify how many vertices are computed per instance
  • added divisor to attributes so that you can specify how many times an attribute is processed per instance
• Buffer Textures
  • added buffer texture support to handle big arrays in shaders
  • reused GLTextureBuffer for this to minimize complexity when updating uniforms
  • set name to GLStorageTextureBuffer to avoid weird naming while still conveying meaning
• Fixed integer types were previously cast implicitly to floating point. glVertexAttribIPointer fixes that by leaving them as integer values.