Initialize 'default' size properly in media edit dialog

Make sure that image model and media edit dialog initialize the
default size properties according to the scalable correctly.
Also make sure that on creation of a new node or edit of existing
node's properties follow on whether the image is set to default
size or custom size.

Depends on the ve-core change:
Ia6bb041bfc050a48d8c40bbff4b73ed2893085e2

Bug: 66149
Change-Id: I6f60fba28e11a111bb40a100148ed1f12d518890
Merge "Initialize 'default' size properly in media edit dialog"