[NX-549] Refactor main supportzip api bits into java classes for simplicity.
[NX-549] Extract supportzip api
[NX-549] Add logger config for supportzip package.  Remove direct dep on nexus-atlas-plugin, no longer needed to contribute to supportzip anymore.
Fix not renamed field
Defer jetty activation by launching it asynchronously and waiting for the internal listener+filter, also update the delegating filter to set status to 503 when delegate is not available.
NEXUS-6692:  Fix url validation and error handling

Changes:
* the regex was too strict, not allowing port numbers nor localhost with paths
* on repo creation, the validation error was swallowed (wrapped into another config ex)
* on repo update the validation was not handled resulting in generic config error
* aligned regex in legacy and rapture UI
Merge pull request #635 from sonatype/NEXUS-6692-fix-url

REVIEW NEXUS-6692:  Fix url validation and error handling
Merge pull request #633 from sonatype/NX-549-extract-supportzip-api

REVIEW: [NX-549] extract supportzip api
Fix repository creation
Add mandatory field to group
Make "browseable" settable for all repo types
Merge branch 'master' into NX-525-shared-database-support