Prefixed all category methods and properties

Class extensions (aka categories) provided by libraries should always prefix their property and method names.

* Unprefixed methods and properties can collide with other libraries and cause weird behavior or crashes (usually causes a compiler warning).
* Unprefixed methods and properties can even collide with private iOS API causing weird behavior or crashes at runtime without prior warning.

In this project there was a conflict with the private iOS method [`-[NSObject safeValueForKey:]`](https://github.com/EthanArbuckle/IOS-7-Headers/blob/master/PrivateFrameworks/AccessibilityUtilities.framework/NSObject-UIAccessibilitySafeCategory.h). It was overwritten by `UIScrollView (SLKAdditions)`. iOS called this method instead of its own implementation which caused an unbalanced retain/release count leading to a crash.