ref(tests): move test scripts under tests/bin

There are several shell scripts in the $PATH on the CI nodes and
also defined in Jenkins jobs directly. This moves them to a central
location under version control for maintainability.
Merge pull request #1702 from mboersma/test-scripts-in-git

ref(tests): move test scripts under tests/bin
feat(tests): add CI node setup script

Adds a new shell script with the incantations needed to get an
Ubuntu 14.04 worker node connected to our Jenkins CI server.
fix(tests): call other tests scripts in local dir by explicit path