JBIDE-16375: Refactor Software page to allow multiple sources
JBIDE-16375: Refactor software page to allow multiple filters
JBIDE-16375: Added filter for early access

Based on the certificationId
JBIDE-16375: Refactoring

* Move inner type to own file
* DiscoveryViewer now extends viewer
* Improved filtering implementation
* License headers
JBIDE-16375: Added support for max version filter

* Improved parallelism on p2 resolver and general performances
* Refactoring to smoother UI (re-use instantiated items instead of
creating them over and over again)
JBIDE-16375: Yellow background for Early-access
JBIDE-16375: Better separation of Early-access option

* Dedicated preference
* Dedicated section in Software/update page
JBIDE-16375: Uninstall when disabling Early-Access

+ Improve responsiveness
JBIDE-16375: Improve disabling Early-Access experience

* Instead of uninstalling, show an information pop-up about current
"hybrid" state
* Remove site referenced by Early-Access connectors so updates won't
reinstall them later
JBIDE-16375: suggeestion for more clear text for Early Access