NEXUS-6182: Simplification of codebase

Still no parallel related changes, just major removal of
unneeded cruft
NEXUS-6182: Improved method name
NEXUs-6182: Get rid of dupe code
NEXUS-6182: Removed state from plx components
NEXUS-6182: Added sync to Image strategy too

not that it matter, as this mojo might be run without
project only...
NEXUS-6182: Initial sleep imple

As the "last" definition is okay (last when topologically
sorted), but, in case of parallel build given last might be
executed with some others assigned on same level. As the
module build durations might be wildly different (ie. some IT
running project vs some last POM-only one), the added code
will simply "hold" (by sleeping) the current thread until every
other project in the build gets some build result.
NEXUS-6182: REshuffled logic

As in parallel builds it's needed to wait for all, and then
evaluate any possible problem in the build.
NEXUS-6182: Moved param creation to proper place.

As the RC goals lost many of them, like polling
related stuff.
NEXUS-6182: Reuse Nx Client in staging mojo
NEXUS-6182: Centralized logging when connected to Nx
NEXUS-6182: More logging cleanup
NEXUS-6182: Proper syncing of critical places

Removed bad synchronized modifiers from method, properly
synced the critical place with a static lock object (that
will assure it is properly synced even in parallel builds).
Added some javadoc explaining stuff.
NEXUS-6182: 10s vs 2s

The sleep period of 10seconds proved to be way too long. So now the
"last in reactor" thread will awake every 2 seconds only to check
are others done, to continue the work.
NEXUS-6182: Sync access to SecDispatcher.

As it's not thread safe.
Merge pull request #61 from sonatype/NEXUS-6182-paralle-exec

NEXUS-6182: Make plugin parallel exec capable