NEXUS-6310: NEXUS-7603: Tika 1.6

Bumps NX Core to Tika 1.6 and removes the customisations added to custom tika XML.
Also, adds the workaround for NEXUS-7603.

Issues
https://issues.sonatype.org/browse/NEXUS-6310
https://issues.sonatype.org/browse/NEXUS-7603

CI
http://bamboo.s/browse/NX-OSSF362