[NEXUS-6626] Upgrade to HC 4.3.4
Add showInfo to master detail (similar to showWarning)
Merge pull request #564 from sonatype/NEXUS-6626-upgrade-to-hc434

REVIEW: [NEXUS-6626] Upgrade to HC 4.3.4
Restoring blobstore-api component; adding OSGi declarations.
Merge remote-tracking branch 'origin/master' into blobstore-plugin