Make translateRange() translate across wrapping transactions correctly

Previously, we would translate to the right of an insertion, but for
wrapping transactions that means we end up with something like
<ul><li>|<p>...</p></li></ul>|, which doesn't make any sense. This
change changes this to <ul><li>|<p>...</p>|</li></ul>.

* Add parameter to translateOffset() that toggles the behavior for
  the offset before an insertion
* In translateRange(), translate start and end differently
** In some cases this can map them across each other, fix that

Change-Id: Ia2197b08d9f6763be3f2db5a59546ddc3f74a281
Merge "Make translateRange() translate across wrapping transactions correctly"