Time column for a release table view, "Show Player" button and more

- Release table view now has a column for displaying total time of
release.
- Added a "Show Player" button so that player window can be displayed at
any time without the need to select a release from table view.
- Changed string representation of Release class to include time
duration and release date.
- Track.Time class refactored into top level class and now supports
durations of time beyond the limit of 86400 seconds.
- Player no longer reloads the same release if this release was selected
from a different tab in search results.
- Few other small changes/improvements.