Several improvements to the code of CPController and its performance

A number of small optimizations to **CPController**, not changing its existing logic, but improving its performance and making its code more compact and easier to read (I hope).

To note specifically: Creating an instance of **NSNumberFormatter** is rather expensive (when done very often), thus it is now created once when creating an instance of **CPController** and then just re-used.

On my MBP I did see a notable improvement in CPU usage during the "no-changes" phase of ControlPlane background run (about 20-30% in average).