Added folder for Theraot.Collections.ThreadSafe
Moved Bucket related files to new folder
Updated HashBucket namespace

HashBucket now belongs to Theraot.Collections.ThreadSafe
SetBucket<T>.Add no longer throws

Instead of throwing Add will return bool, this will facilitate wrapping
SetBucket<T> in ISet<T>.
Added some interfaces

Looking forward to optimize Contains
Added explanation on TODO comment
Allows to IEqualityComparer<T> from a IComparer<T>
SetBucket now implements ICollection<T>
Style fix
WeakEvent and required stuff to make it work

- Updated WeakDelegateNeedle
- Added WeakSet
- Added WeakDelegateSet
- Added WeakEvent
- Added GCMonitor [Provides "Garbage Collected" notifications]