Several QOL improvements

[computablee]

Here is a list of everything changed in this PR:

• removed the Locking class and merged everything into DotMP.Lock
• Shared<T> now implements IDisposable
• created SharedEnumerable<T,U> which overloads the [] operator for easy use of shared enumerables
• created factory methods for both Shared and SharedEnumerable objects
• nested parallelism now triggers an exception
• nested for or for-reduction loops now trigger exceptions
• added a K-nearest-neighbors example
• moved the Schedule enum out of the Parallel class to reside directly within the DotMP namespace
• updated documentation to reflect all of these changes