Enable pass-through of authz ctx to hbase (1/x)

The idea behind this and follow up commits is to enable Lily to pass on an authorization context to a hbase-based authorization framework by NGDATA (not part of the OSS Lily DR).

 * define a thread-local based authorization context holder
 * wrap tables in AuthEnabledHTable to make sure authz context is passed on to hbase for each request
 * testcase

introduces a dependency on lily-hbase-authz-public-client which is not yet publicly available but will be soon.

not yet / todo: make the same work for the remoterepository, i.o.w. modify rpc protocol to pass on authz context
Merge branch 'master' into authz
Use branch-specific artifact version
Merge branch 'master' into authz
Add hbase-authz-public-client

These are some client helper classes to interact with the NGDATA hbase authorization layer.
Merge branch 'master' into authz
Fix lily-hbase-authz-public-client dep
add extra client attrs for hbase-authz

Introduce some extra attributes that the AuthEnabledHTable passes on to the authorization coprocessor.

Some code refactoring.
Do not add nv recordtype kv twice

put.add will happily record the same KV multiple times. This can be annoying/confusing on the hbase side (e.g. in coprocessors).
Adjust permission format

Adjust permission format in DEFAULT_PERSSIONS to the new syntax expected by hbase-authz.
change security label things

Security labels are now a single string, and are now stored in a column familiy + qualifier selected by the application on a per table basis, the name of the CF&Q is stored in the table descriptor.
The setSecurityLabel method had become absurdly trivial, so removed it.
javadoc clarifications
add source artefacts to build, install and deploy to nexus
removing snapshot repository
Add constant for lily.sec.label.encoding
LILY-2524 Add utility for subtype checks

This is similar to RecordUtil.instanceOf, but takes two types as argument, thus it is a is-subtype check rather than an instance-of check.
forward-port repository changes from master
forward-port avro version change from master
merge authz branch into master
fix version in hbase-authz-public-client