* Fix some warnings in examples.

* cleanups from review

Co-authored-by: Jeffery Myers <JefMyers@blizzard.com>

Some enums values have been renamed to be more consistent and also provide a more detailed description:
 - ShaderLocationIndex:    LOC_VERTEX_POSITION -> SHADER_SHADER_LOC_VERTEX_POSITION
 - ShaderUniformDataType:  UNIFORM_VEC2 -> SHADER_UNIFORM_VEC2
 - MaterialMapType: MAP_ALBEDO -> MATERIAL_MAP_ALBEDO
 - PixelFormat: UNCOMPRESSED_GRAYSCALE -> PIXELFORMAT_UNCOMPRESSED_GRAYSCALE

- Renamed Begin3dMode() --> BeginMode3D()
- Renamed Begin2dMode() --> BeginMode2D()
- Renamed End3dMode() --> EndMode3D()
- Renamed End2dMode() --> EndMode2D()

It's more educational to go through new material system, so, I decide to
remove this function to avoid students confusion...

Examples have been renamed for coherence with raylib modules and test
examples have been merged into examples folder.

Check CHANGELOG for a detailed list of changes

Check CHANGELOG for the list of changes in this release!

View CHANGELOG for details