- Refactored of the code
- Created getters and setters for easy customization
- Made the + and - buttons going to minimum/maximum value when they are
 out of the index range of valueArray 
- Added note at the top of the class
- changed setSelectedStep to take care of round trips if the step is set
by code or by seek bar
- moved generation of the value array to the main activity
- added setSelectedStepForValue so it is possible to set the selected
step manually. Useful for setting the start value and step
- added save and restore the instance state in case of orientation
change
- Made the buttons continue increasing/decreasing when long pressing
- Added setter setButtonChangeInterval() to set how many steps should be
changed when pushing the buttons
- Added setter setValueUnitName() for setting the unit name of the
values. This name is displayed in the second text line in the middle of
the circle
Buttons continue to change values on long press