Update VE core submodule to master (c150259) for scalable changes

ve.dm.Scalable is now a computational model for image scaling and
size manipulation. This commit adjusts the nodes and the edit and
insertion dialog to handle the new scalable model, and by that
use a centralized computational engine for all scaling and size
changes.

New changes:
3ec19fb8 Refactor Scalable functionality

Change-Id: I017a017924f544cc8bc9b7d8245335759ae0e890