Discovered that using this kind of code:

```const { MY_SETTING } from settings;```

means that changing settings properties has no effect as the objects
are being set before the user changes them.

# Conflicts:
#	src/core/Shader.js
#	src/core/renderers/webgl/filters/Filter.js
#	src/core/sprites/webgl/generateMultiTextureShader.js
#	src/extras/webgl/TilingSpriteRenderer.js
#	src/mesh/webgl/MeshRenderer.js

Fixes jsdoc issues with exports and module.exports

* Made const that are setting writable

* Moved more items to the settings

Build System, Babel and ES6 src

* little filter-fix

* removed space

this way we can cache setting of stuff

added the precision check to the gl core object

Dev vao state cache

* minimal texture bounds pass 1

* cheeky opts

* tidy up code

* create empty textures

* added empty texture

* couple more tweaks

* fixed empty texture issue

* fixed tweaked so id's sit on glTexture

means it should work on multiple contexts

* tweaked unbound textures

* tidy up

* upped max textures to 4 for mobile!

also sending state to tiling sprite VAO

* removed _activeTetureLocation

* tweaked eslint

* make sure buffer is bound

* updates based on @englercj review points

- Added vertexCount back in as it still yields much faster results in
iOS
- Tidied old comments
- Replaced i++ with ++i

Looks like since we call loseContext() on `WebGLRenderer#destroy()` that
if you create another WebGLRenderer with the same canvas the browser will
recycle that lost context and return it.

This means when we try to use the context it is actually in a lost state.
This change tries to restore a lost context before we use it. It also adds
a debug assert at one location that will be invalid if the context is
invalid.