Viewer status bar redesign

[rotbus19]

Currently, the Viewer status bar takes up the entire width of the screen but contains only a small amount of information - most of it is 'dead' space. Suggestion:

1. move zoom controls to top toolbar (keep status bar for information only)
2. make status bar only as wide as the content it contains
3. make status bar 'float' on top of image so now image extends to bottom of window
4. now user can set opacity of status bar as preferred to see image underneath it