Font padding fix fix (playcanvas#1606)

[FIX] Particle system component now listens on all asset events (play…

…canvas#1603)

A hotfix for sprites batching drawOrder (playcanvas#1594)

Library code assets (playcanvas#1566)

* Set asset to loaded if it's a library script

Text-element render sub-range (playcanvas#1585)

* added text-element sub-range
* using two separate properties for range start and end
* expose range start and end in ElementComponent
* small doc update

Revent hierarchy sync optimization.

AssetListLoader (playcanvas#1582)

Fix syntax error

Add missing button sprite assets used in the example code (playcanvas…

…#1575)

Revert negative scale fix.