[JENKINS-23552] Replace "Allow priorities directly on Jobs"

 * Added new JobProperty Strategy
 * Removed code for special handling of priorities on Jobs
 * Only show the JobProperty if some JobGroup is using it
 * Removed the checkbox on the main config page
Refactoring

 * Dropped "cloudbees" from class names 
 * Added Licence headers
 * Updated @since to reflect target release verion
[JENKINS-23552] Replace "Allow priorities directly on Jobs"

 * Moved and renamed "AdvancedQueueSorterJobProperty"
Refactoring, moved the PrioritySorterJobColumn
 
 * everything in hudson.* is deprecated