Polish display and evaluate animation

Bug: 20915670
Bug: 21489377

- Adjust font metrics across all supported device configurations to
  support font scaling and min touch size requirements.
- Support proper font scaling for non-scrollable results when performing
  the evaluate animation.
- Remove restriction for only using 4/5 of the width of the result
  display (NOTE: the result's textSize must match the formula's
  minTextSize).
- Add AlignedTextView base class to ensure formula/result padding is
  based on the displayed text's ascent/baseline.

Change-Id: Id53e9bdc6e699fb05fdf331a6a472ecc170edf38