Fix regression from the ARC conversion. Change the raw, unretained
pointers in ASControlNode to weak references. Use NSMapTable instead of
the pointer-as-NSValue system.
Summary:
* Fixes#3
* Ordering: atomicity, then [optional] readonly, then value semantics (retain/copy/assign)
* Removed redundant `readwrite`
* No spaces between "getter = name" ("getter=name" instead)
* Property method overrides renamed as well
* self.isBlah, while technically not entirely correct, still resolves to [self blah], so left alone (@kimon had advice on this sort of naming issue last summer), and largely inconsequential
Test Plan:
* Compile and run
Summary:
* Moves ASThread.h from Private to Public visibility
* Moves ASThread.h from Private/ to Details/
* Changes public #imports from "" to <>
Test Plan:
```
#import <AsyncDisplayKit/ASDisplayNode+Subclasses.h>
#import <AsyncDisplayKit/ASControlNode+Subclasses.h>
```