WebGLRenderer: Tweaked drawRange/groups handling. As per @WestLangley suggestion in 06893919.

@nraynaud do you mind double checking that I didn't break anything?

support WEBGL_color_buffer_float and EXT_color_buffer_half_float
also fixed a cleanup bug were the function would exit leaving the wrong buffer bound

Added call to _renderer.resetGLState() at the end of light loop in WebGLShadowMap.render(), updated WebGLRenderer.refreshUniformsShadow() to send inverse of point light position to shader. Fixes #7260.

Bug fix: Viewport not restored correctly when rendering point light shadows for scenes that contain multiple light types.

Green refactor of Render-to-texture: Use a Texture instance inside WebGLRenderTarget rather than duplicating all internal texture fields.

Fixed morphing, broken by #7236.

Includes more robust handling of custom materials (see #7153).

Updated cubeToUV() to a reduced-instruction version with minimal branching, and updated near plane values for shadow map cameras to be at least 1.

Point light shadow mapping now utilizes cube-to-2D projection, avoiding the need for a samplerCube in the shader.