Fix FDN back button, restyle screen.

While fixing the original, there was a bunch of jank and inconsistent
styling I noticed on some of the FDN settings screens, so I tried
to clean it up somewhat.

+ Fix non-functional button on the GetPin2Screen, which was the
original bug.
+ Fixed underline tint color on the GetPin2Screen.
+ Moved text labels into EditText hints on edit/pin2 screens.
+ Updated margin/alignments, consolidated layouts to be simpler.

Bug: 18410153
Bug: 19285837
Change-Id: I6748a924615120173fa3ced57ed01c68464c8044
4 files changed