Blender Git Loki

Rename Scene's embeded collections from "Master Collection" to "Scene Collection"

Note that this name is essentially never used anywhere, besides as 'information'
mostly accessible from python console. Those embedded IDs are not in Main, so they
are not accessible by name ever, and mostly unusable from animation perspective
(either drivers or fcurves).

Therefore, no breakage is expected in user scripts or addons, nor when
loading in older versions of Blender.

Reviewed By: dfelinto, brecht

Differential Revision: https://developer.blender.org/D11812