many small improvements to test ecosystem

This pull request contains a lot of tidying up of existing code and documentation regarding the various test suites.  Highlights are:

* adds support for Gemfile.d and routes.d plugin mechanism (requires crowbar/barclamp-crowbar#419)
* test suite dependencies are now handled via bundler from the central `Gemfile` rather than hardcoded (helps fix `rcov` / `simplecov` clashes between Ruby 1.8.x/1.9.x)
* vastly improved devguide docs
* sync travis-ci/update-git.sh with latest code so Travis CI should work again (still needs a replacement for James' VM with cron job)
* deprecation of existing `./dev *-test*` subcommands in favour of a new `./dev tests` subcommand (fully documented in `doc/devguide/testing*`)
* various bug fixes
* make ./dev more helpful
* make code coverage reports more easily accessible
* break down some overly long functions in ./dev