Separate TaskView translationX into dismiss + offset translations

- Previously, these both setTranslationX() directly, meaning one
  could clobber the other. Now they are set independently and
  aggregated to setTranslationX().
- For fake landscape, we actually are setting translationY, so
  had to create both translationX and translationY properties, and
  set the appropriate one via the current orientation handler's
  "primary" dimension.

Fixes: 176766821
Change-Id: I00ed0bd73dbea00f4018de62260ed35f4d6966a5