Made MaxAngle and MinDistanceSquared customizable via initializer

I'm currently working on a project where i need this two values to be customized by the application.

So I converted the two constants to private properties which can only be set using an initializer.

Added initializers:
```objective-c
- (id)initWithFrame:(CGRect)frame maxAngle:(CGFloat)maxAngle;
- (id)initWithFrame:(CGRect)frame minDistanceSquared:(CGFloat)minDistanceSquared;
- (id)initWithFrame:(CGRect)frame maxAngle:(CGFloat)maxAngle minDistanceSquared:(CGFloat)minDistanceSquared;
```