NexusClient had UA carrying fixed 1.0 as version.

This made us unable to distinguish properly between clients
(like in case of staging) to differentiate between different
versions of Staging client.
Merge remote-tracking branch 'origin/master' into nexus-client-version
Default client version is "unknown" if
not able to load up.
Updated since tag
Added UT for version

And fixed the wrong binary name of the maven properties
UT javadoc and method rename.

To better reflect what this is about.
Merge pull request #790 from sonatype/nexus-client-version

[2.5] NexusClient UA should carry proper version