NEXUS-6090: Getting rid of SISU Velocity.

That introduced component based configuration
for VE. Using plain provider pattern, as the
SISU Velocity was basically doing that same,
except in "plx way".

Changes:
* banned sisu-velocity from build
* upped goodies and mailer dependencies (that has needed changes too)
* removed SISU Velocity related code from Nx core
* introduced Velocityengine provider
* adapted restlet1x internals
* adapted VelocityContentGenerator
NEXUS-6091: RequestContext cleanup

Before RequestContext was introduced (around 1.0.x of Nexus)
it was a plain Map<String, Object>. This change makes req ctx
not a map anymore, and contains handful changes across whole Nx
to fix it's misuses as map.

Also, a UT introduced that verifies how context is properly
passed on as expected.
Merge remote-tracking branch 'origin/master' into NEXUS-6090-velocity

Conflicts:
	buildsupport/goodies/pom.xml
Fixing licenses

As these sources are moved and modified from terminated
sisu-velocity.
Merge pull request #247 from sonatype/NEXUS-6090-velocity

NEXUS-6090: Getting rid of SISU Velocity.
Merge pull request #248 from sonatype/NEXUS-6091-request-context

NEXUS-6091: RequestContext cleanup
Merge remote-tracking branch 'origin/master' into NEXUS-6027-remove-deprecated-classes