Fix for #2557 , backport from pixi-v4.

added removeItems; added unit tests; replaced uses of original splice with removeItems

js lint

Tweaks to Container ...

- addChild now accepts multiple children as an argument
- addChild is now also twice as fast
- removeChild now accepts multiple children as an argument to be removed

filters might be an empty array

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

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.

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

more doc tweaks

more doc tweaks

fixed extends doc issue

minor cleanup of destroy methods

fixed cachAsBitmap issue

fixed getBounds on Sprite ...

sprite getBounds now takes sprites children into account

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

Docs docs docs

massive jsdoc fixes

Docs, mostly the display and graphics folders and some filetype update

Fixed up cacheAsBitmap ...

Now works nicely with filters.

cached getBounds each frame ...

handy for all sorts of things!
removed ‘isMask’ as ‘renderable’ provides a more flexible approach