Adds tint support

[mathieuanthoine]

Add tint support in the exporter.

AS3 runtime has to be modified to manage it.
There will be a flump-pixi-runtime (haxe) version soon.

[tconkling]

Hi @mathieuanthoine, thanks for jumping into this. Tinting support is a good feature to add.

Could you please make sure your commits follow the Flump coding style? My initial concern with these pull requests is that they use tabs instead of spaces and they occasionally don't follow the project's variable and function signature conventions.

That said, for this pull request specifically: why is the tint an Array instead of two separate variables? Is that to support nullability? This should be documented (also document the variable types of the members of the Array).

[mathieuanthoine]

Hi @tconkling, I have converted tabs to spaces.
What other variables or functions signatures don't fit ? I've tried to be as similar as your code.

Concerning the tint, I chose to use an array instead of two differents properties because these are the two components of a same behaviour.
I haven't chose to create an object with two named properties to avoid verbosity and inflate the file size.

[mathieuanthoine]

tinit support available on pixi-flump-runtime