Revert "update mask transforms; fixes #1978" ...

This reverts commit c8244ed.

update mask transforms; fixes #1978

hint free; checked out bin from upstream/dev

Merge pull request #1992 from bchevalier/particleContainerRefactor5 ...

[Enhancement] Improved performance of adding and removing particles

Massive documentation update; fixes many issues. ...

Issues fixed by these documentation updates:

- #1973, fixed filter and BitmapText property docs
- #1908, fixed type reference links
- #1856, fixed name of MeshShader

* Improved performance of adding and removing particles to ParticleContainer

Merge pull request #1925 from mreinstein/dev ...

update stale DisplayContainer docs. Remove broken normal filter.

Add callback for when children change; #1988 ...

This is a rebase of the commits in #1988 to squash it down to a single
commit and remove the extra merge commits in @bchevalier's repo.

update docs to reflect sprite support in v3 #1639

send Container as reference on added/removed events. #1870

trigger 'added' and 'removed' events for Container children.

manual merge of #1826; fix generate texture scaleMode

fix small doc comment

more doc tweaks

more doc tweaks

fixed extends doc issue

fixed generate texture parameter issue

remove some private docs

update for new event emitter api

minor cleanup of destroy methods

fixed cachAsBitmap issue

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

fixed getBounds on Sprite ...

sprite getBounds now takes sprites children into account

rework v3 to use EE3 instead of a custom emitter

Fix all the remaining jshint stuff

Fix recursive destroy children

Tidying up some stuff

Added destroy methods and fixed sprite bug #1505

Strip and rope docs, and usage examples

Put most rendering code in _renderCanvas to match _renderWebGL