- Use compund drawable instead of an imageview
- Reset compound drawable every time so that viewholders being reused show the correct confidentiality status

- Show the icon in list of issues if issue is known to be confidential

- Show confidential icon as a compound drawable if issue is known to beconfidential
- Modify string resource to include issue number for easier formatting

- Add new values to colors, strings and styles

Added an CircularReveal dependency (https://github.com/ozodrukh/CircularReveal) for
compat reasons (native supports from API 21, and this supports from API 14). We could
use this lib in other parts of the system too, it's easy to use...