Simplification of slider state fixing some bugs

[bimms]

• Refactor the handling of the slider state using turning angle
• Fix undesired hour increment at 12:00 position
• Fix undesired display at/around 12:00 position, e.g. emtpy string
• Fix sliding from 0 min. to the left, resulting in 59 min.

Motivation/Issues:

• Sliding across the 12-o-clock position caused the hour counter to increase. When going back and forth, the hour increases multiple times. I saw issue #7 and its reference to #8, but problem remains.
• Slowly sliding across the 12-o-clock position in minimal steps can result in different undesired displayed durations, including empty string (then, only "min." is displayed).
• It was possible to slide to the left, starting from 0 minutes. Resulted in 59 minutes.

Changes made (old code still contained, commented out):

• Refactoring to handle the slider state simply as a turning angle, which may be larger than 2 pi (i.e., not handling full hours separately in the first place)
• Whenever minutes/hours are needed, convert turning angle by means of a simple coordinate transformation (full 2*Pi of the turning angle represents hours, rest represents minutes)
• Removed unused const variables

Remaining issues:

• Tapping (instead of sliding) has not been considered
• snapToMins has not been taken care of (should be trivial)
• Should rename "multiplier" to "hourHand" (in parallel to "minuteHand")
• Even in addition to the commented-out code, there is surely further code removal possible (simplification)
• Didn't work myself into the animation stuff. Simplifications of update rules might be possible.

[cdharris]

Thanks for looking into and simplifying some of this @bimms :) Will review further when I get some time towards the end of the week. Cheers!

[Skyost]

@cdharris Any news on this ?