fix rendering problems with mesh and rope

Fix Mesh Rendering to enable pixi-spine Mesh to render properly

fixed extends doc issue

update indices data before drawing

Move items into their namespace ...

This commit also:

 - fixes some dangling whitespace,
 - fixes some incorrect docs in extras/mesh,
 - moves Text to core
 - moves BitmapText to extras
 - moves math constants to const.js

Fix all the remaining jshint stuff

Moved the mesh folder to the root