- No default VR device parameteres inside raylib
- VR device parameter should be provided by user
- VR distortion shader should be provided by user

Some tweaks

Multiple functions added and some reviewed to adapt to the new multi-mesh, multi-material and animated models.

This is quite a big change, Model struct has been redesigned to support multiple meshes and multiple materials, most 3d fileformats contain multiple meshes and reference multiple materials.

Consequently, multiple functions have been reviewed.

LoadOBJ(), LoadIQM(), LoadGLFT() now return a Model.

Current LoadOBJ() is not valid anymore, actually, tinyobj_loader_c library is considered for replacement.

Probably uncomplete, not tested yet...

Function provisional renaming... that's not the end of this issue...

Following raylib notation rules

This specific change could be very annoying for people already using FLAG_MSAA_4X_HINT, their programs will compile correctly but window won't be shown...

- Unsigned int not supported on OpenGL ES 2.0 -> Removed
- Reorganized enum -> Removed BOOL (not uniformType)
- Support sample2D uniform type

Same functionality could be achieved using FLAGS... but also considering removing raylib logo animation...

Decided to allow user to provide values directly instead of requiring a Vector2 struct, probably more confortable to use.

 - SetMousePosition()
 - SetMouseOffset()
 - SetMouseScale()

- SetMouseScale changed to take in a Vector2.
- Added mouseOffset global which is used in mouse read functions.

- Changed mouseScale to Vector2.
- Added SetMouseOffset to change XY of mouseScale.