Replace deprecated assembly:aggregates w/ :single

Maven-assembly-plugin's "aggregate" goal has been deprecated for a
while, and it's generally badly behaved.  It forks the build
repeatedly when I try to build the entire TP3 reactor project, and
this gets worse when it interacts with javadoc:aggregate, which also
badly behaved and repeatedly forks the project.

maven-assembly-plugin is easier to fix than javadoc, because they've
deprecated the :aggregate goal and provided the new :single goal which
is essentially functionally identical but doesn't fork.
Initial commit of javadoc-to-S3 pom config

This runs javadoc:aggregate and uploads the results to the same S3
bucket as the asciidocs when the profile "javadoc-upload" is enabled
by setting either -Djavadoc-upload or -Pjavadoc-upload when invoking
mvn.

This has at least one known annoyonce: javadoc:aggregate forks the
build, and source:jar also forks the build, so the javadocs get
generated twice.
Replace source:jar w/ :jar-no-fork in pom.xml
Exclude gremlin-test from uploaded javadocs

With -Djavadoc-upload, this maven-javadoc-plugin configuration
generates a bunch of warnings about unresolved dependencies for
external code (e.g. hadoop, giraph).  All of the TP code javadoc needs
to generate internally-consistent output is present, but javadoc
whines about being unable to resolve imports of 3rd-party code.  These warnings can't be turned off.

These warnings could probably be suppressed by creating a new module
that depends on all the others except gremlin-test, then running the
javadoc plugin from the new module.  We'd have to be careful not to
accidentally upload this dummy module's empty jar or useless pom to
Sonatype though.
AsciiDoc S3 upload config should not be inherited

This prevent TP3 submodules from trying to upload AsciiDocs to S3.
Only the parent module is responsible for that.  Having submodules
attempt to do it is harmless in that it generate an error or result in
multiple uploads -- the submodules think there are no files to be
uploaded and hence just do nothing -- it could be confusing.
Merge remote-tracking branch 'origin/master' into javadoc-s3
Update readme for deploying javadoc.
Make docs upload to version and current based s3 directories.
Merge remote-tracking branch 'origin/master'