BitmapFont loader fix (#5027)

Creates unit-test and improves single and multiple image font loading (#4951)

Fixes Multi-Texture BitmapText Fonts (#4932)

Support for multiple textures for single bitmap font. (#4641)

Remove duplicated base url from loader path in the bitmapFontParser (#4101)

Refactors the spritesheet, texture and bitmap font loaders (#3676) ...

* Refactors the spritesheet, texture and bitmap font loaders

* Fixes trailing space

* Addresses feedback in var caching and docs

* Adds unit test for Texture.fromLoader

* Adds new Spritesheet class

* Cleanup spritesheet destroy and imports

* Added baseTexture destroy to Spritesheet

Update to Resource loader v2; fixes #2876

expose bitmap font parse, fixes #2196

clean up to be specific

Huge refactor to match a new shiny eslint file.

Prefer const (#3002) ...

* added prefer-const rule to .eslintrc

* eslint const autofixes

* manual let to const changes; lint free;

* added brace style 'allman' to eslintrc

* brace style, comment fixes and default arg

* brace style fixes

* more brace styles

* Point default args

* Point brace styles

* Observable Point default args

* more brace styles

* jsdoc comment style

* brace style

* brace styles and small jsdoc fix

* brace styles

* removed unneeded eslint inline comment

* brace styles; lint free

some more es6 changes (#2969) ...

* some more es6 changes
- const instead of let if possible
- arrow functions
- string templates
- argument defaults

* object property shorthand

* some more es6 changes
- const instead of let if possible
- arrow functions
- string templates
- argument defaults

* Revert "Merge branch 'dev-es6-sb' of github.com:stbaer/pixi.js into dev-es6-sb"

This reverts commit 8d3af81, reversing
changes made to e8b9948.

* Revert "Merge branch 'dev-es6' into dev-es6-sb"

This reverts commit 3eeaf79, reversing
changes made to fb69536.

* Revert "Revert "Merge branch 'dev-es6-sb' of github.com:stbaer/pixi.js into dev-es6-sb""

This reverts commit c860228.

* fix RenderTexture, incomplete merge

* fix for text font properties

* reverted some changes

* checked out License, Readme and Contributinf from dev-es6

* editorconfig updated: 2 spaces for .eslintrc

* added eslint rule: spaces around fat arrow

* used eslint fix for consistent spaces around fat arrow

* don't allow scale.x or scale.y to be 0 in displayObject setTransform

* removed jshint comments (again)

Update imports and exports, getters and setters

Disallow the use of `var`

Fixed trailing slashes for xml font files' images (#2680)

Fixes loading bitmap fonts from data URIs (both FNT and Image)

fixed kerning undefined error

Changes for pixi-compressed-textures ...

1) newer version of resource-loader
2) pass the metadata to images
3) export WebGLManager

Depecrate `PIXI.math` namespace ...

Access math members from PIXI when outside of core, require the math module directly when inside of core.

Remove the rest of internal module coupling between packages

less ducktyping, use is* from loader; fixes #1628

Merge remote-tracking branch 'origin/dev' into dev

fix some bugs in the loader

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 loading of bitmap font

get relative bitmap font loading properly.

better detection of bitmap font; should be relative to xml url now

loader already passes baseUrl, don't need to do it in add

Docs fixes, improved the consistency of the deprecation, thanks @englercj ...

Also added a comment on the bitmap font parser, will leave the change
until we find a new caching system

fixed typo in cacheAsBitmap, fixed bitmap text and restored the font cache so we can debug it