NEXUS-6310: NEXUS-7603: Tika 1.6 and bugfix

Forward-port+squash of commits:
7514b292756b703a6f9916247e8f7581efc676de
b310d16abcf3ee59baa4a7714acec489152cd09f
f1c515e581b3759526f65eee2ed8e32c0b9c86f6
7f743643da65dc4627ded263af6dd88666d95f9a

Original PR already merged
https://github.com/sonatype/nexus-oss/pull/836

Sanity CI (as thing did change in this area)
http://bamboo.s/browse/NX-OSSF370