Use units within ROIs
Integrated units objects furthermore
Had to move UnitType to package util.ui
Code formatting, removing of unused imports
Handle the case that there is no pixelsize given

In that case, just sets 1px as pixel size
Use unit symbols from API
Use lookupSymbol() method from api
Replace 'null' with '0' when showing line angle
Make sure same units are used for distance calculation
Cosmetic changes (code formatting, java docs)
Fixed: Missing values in results table
Use "calibrated" as menu item name instead of "in Microns" etc.
Fixed some more minor issues:

- Angle of "0" wasn't shown in results table
- Degree symbol missing
- Accidentely commited System.out.println()
Merge pull request #3229 from dominikl/roi_use_units

Use Units in ROI/MeasurementTool