Major repo layout and pom refactoring

This commit collects experimental release-engineering commits from the
fork github.com/dalaro2/titan, plus some additional commits from my
local repo.  I used a fork under the bogouser dalaro2 while
experimenting with release automation to keep my credentials separate
and reduce the likelihood of unintentionally pushing a "release" of
titan.  However, the dalaro2/titan commit history is noisy and
confusing because of all the fake releases and revert commits that I
made while testing.  The net changes are fairly small when expressed
as a patch between the common ancestor commit in titan03
(771fb4e10a2494c6569a210a16f8d3187aa4ae87) and the fork head, so I'm
collecting them into this new commit rather than pulling history from
the experimental fork.

The most important operational note about this commit relates to the
doc directory.  doc is no longer contained inside the titan repo.  doc
now points to the titan wiki repo using git submodules.  Furthermore,
all images used in the wiki that used to live in gh-pages now live in
the images folder inside the wiki repo.

There's a lot of documentation for git-submodules, but the cliffs
notes are something like:

* after cloning titan, do "git submodule update --init" to get doc
* when switching from a branch with submodule doc to a branch with
  the old doc directory, you may have to first "rm -rf doc"
[maven-release-plugin] prepare release 0.3.2
[maven-release-plugin] prepare for next development iteration