[NEXUS-6276] Avoid NPE's when nexus.log is not yet available
NEXUS-5987: Routing fixes

Changes:
* removed "applies to user managed reposes only" limitation
* removed use of ancient "validator", migrated what was needed from it
* updated logging and other issues found in class
Merge pull request #403 from sonatype/NEXUS-6276-npe-log-tab

REVIEW: [NEXUS-6276] Avoid NPE's when nexus.log is not available
Handle legacy and modern url connection content-length, prefer modern response
Notes about unifying resource impl
complain if resource.size < 0
Merge remote-tracking branch 'origin/master' into timeline-kazuki
Restore behaviour where we only scanned a subset of plugin dependencies
Merge pull request #388 from sonatype/NEXUS-5987-routing-user-managed-reposes

NEXUS-5987: Routing fixes
[NEXUS-6327] Fix virtual template name used in UI
Merge rapture (NG UI) branch
Merge remote-tracking branch 'origin/master' into timeline-kazuki