Adding Different Queuing Strategies

_The changes moves to Priority Sorter to 2.0-SNAPSHOT_

* "Legacy" is still supported and the Plugin will in "Legacy" mode still behave like 1.x versions.
* Converting to "Advanced" mode will preserve relative priorities.

*In "Advanced" mode:*
* Configurable number of priorities
* Configurable Default priority
* Set priority on Jobs based on View and/or job-name filter (new Action/Page on main page)
* Option to allow or prevent setting Priority directly on Jobs
* Option to select priority-sorting algorithm between:
 * "First In First Out" (jenkins basic approach)
 * "Absolute" (what Priority Sorter does today) 
 * "Fair Queuing" (equally distribute resources over a number of "buckets")
 * "Weighted Fair Queuing" (weighted distribution of resources over a number of "buckets")