(bug 45423) Create SurfaceFragment.isolate method

This method will take a selection of siblings and ensure they
are the only chlidren in their first parent which can be placed anywhere
(for example the first parent of a tableCell which can be placed anywhere
is a table, and for a listItem is a list).

The method ensures no redundant empty tags are created, so if
the selection encompasses all siblings then no action is taken.

Also in this commit are two test cases run against ve.dm.example.isolationData.

Change-Id: I783bd5ecd9d43d61f9b2685985409b4d746cbe94
Merge "(bug 45423) Create SurfaceFragment.isolate method"