Add insert and remove events to MetaList

These events occur when an item is inserted or removed by onTransact(),
so both for insertions/removals done through the MetaList mutators and
insertions/removals done by any other means.

We have to gather these events and batch them up because we have to allow
offset translation and index recomputation to occur first (otherwise
calling .getOffset() and .getIndex() on inserted items doesn't work).

Change-Id: I74a9a21398eca4e9afd7148171af20d439cf7ebd