Rename back button to navigate up button

Also some minor wording changes.

Test: Rebuild apk
Bug: 219000314
Change-Id: I9e54bd5f17dd1eb4e0f8803d2c29781a49c1124d
Merged-In: I9e54bd5f17dd1eb4e0f8803d2c29781a49c1124d
2 files changed