Add 'clone' and make 'getDimensionsFromValue' static in ve.dm.Scalable

This is the first step to making sure that editing images is done
without affecting actual dm nodes. Make sure the scalable can be
properly cloned; also, make getDimensionsFromValue a static method
that can be called for calculations without having a scalable instance.

Change-Id: Icd5c37f0df5d6c89a9befcbfdeaf26ce15ab7108
Remove lies from documentation

Change-Id: I28d57afba967f58a7a8beff561acf42b2b77f1c7
Merge "Remove lies from documentation"
Merge "Add 'clone' and make 'getDimensionsFromValue' static in ve.dm.Scalable"