Refactor Queue to aggregate NSOperationQueue

Now exposes accessors for global shared queues for each kind of Quality of Service.
Fix compiling Queue
Delete Test target
Provide names for shared Queue instances
Queue.Current returns existing global queues
Refactors building full Queue name + marks
File for Swift extensions and Operation class
Optional fallback operator
Revert back to NSOperationQueue extension

It was not possible build a layer above NSOperationQueue with generic NSOperations and so on. Extension approach will serve the best purpose.
Provide some default values for convenience init
Return back basic `perform` methods
Refactor default operation behavior
Return back delayed perform
Write more demo code
Update README with latest changes

Migrated from using GCD queues to NSOperationQueues, mostly.