Added some Android L specific UI changes

- added a custom color for the Navigation Bar that also takes the
getDarkVibrantColor from the image palette in TaskEditFragment.
- added elevation + size animation for the task CardView when long
clicked
- cleanup + resources (dimens)

Added custom TaskCard view

- the TaskCard view subclasses FrameLayout (which is CardView’s super
class);
- animation code moved inside TaskCard.

Resolved merge conflicts