NEXUS-7761: Forward-port of "DirSupport.move simplification"

Commits (from 2.11.x):
e9c3d195ccb298c445549367c22fe076705d548c
63c3216b1a92e24d7e11b83f58f9cef20d43eb16
3a1021fed73b1be021f4e3ebe21e124ee54b49d9
7a1dee7b1304a65a1d247367a4f1932c786999cd
13ec6b7dd2c44beabc5370652b4e26f1cd3c378a
f3732eb2105e2a21554d69311d12a5df8395e275

These above contain PR but has more than the PR
https://github.com/sonatype/nexus-oss/pull/772
Merge remote-tracking branch 'origin/master' into dirsupport-move-simplification
Use delegated call, do not call it directly

As the handler has means to break endless
loops by inspecting is path requires managed
attributes or not.

Original commit:
7afbca747265bc8a42c1559e22ea701c2b5802dd
Merge remote-tracking branch 'origin/master' into dirsupport-move-simplification
Merge remote-tracking branch 'origin/master' into dirsupport-move-simplification
Removal of redundant Tasks-related imports
Update maven-jaxb2-plugin to 0.11.0 (fixes 'file' access on Java 8)

An alternative solution is to use the properties-maven-plugin to set
"-Djavax.xml.accessExternalSchema=file,http" which is still required
for modules that use the jaxb2-maven-plugin.
Merge pull request #901 from sonatype/dirsupport-move-simplification

NEXUS-7761: Forward-port of "DirSupport.move simplification"
Add task ID
Remove println, use logging
Merge remote-tracking branch 'origin/master' into NEXUS-7789-scheduling-api