Code improvements

There is no logical changes.
Only code-cleanup.
Here the main changes:
- move all "magic numbers" to explicit-named constants (enums). It should simplify future development process and eliminate potential mistakes.

- replace magic numbers to standart enum values like `0 -> NSTextAlignmentLeft`

- update code to modern syntax like `[NSNumber numberWithFloat:labelYAxis.center.y] -> @(labelYAxis.center.y)`

- rename ArrayOfValues to arrayOfValues according apple coding style guides.