Introduce context object in getDataFromDom()

* Introduce context object as specified for
  ve.dm.Node.static.toDataElement()
* Remove wrapping variable in favor of context.wrapping
* Remove wrappingIsOurs in favor of context.canCloseWrapper
* Introduce originallyExpectingContent and use it to repopulate
  context.expectingContent after closing a wrapper
* Replace most uses of branchHasContent with context.expectingContent
** Except for two cases where we need originallyExpectingContent

These changes fix a case where a metaBlock was generated in an inline
position. Updated the tests to reflect this.

Change-Id: I6baf6053f8a3a0b7d91487f812b9235a7b2b3db1
Merge "Introduce context object in getDataFromDom()"