Use Ansible script to update test server

[bertfrees]

Some work may be needed to make the pipeline-webui deb package fit our needs:

• [x] check if database is not lost after upgrading
• [x] make sure stopping/restarting the service works (https://github.com/daisy/pipeline-assembly/issues/79)  (EDIT: starting/stopping web UI is currently done with a custom script in test-server-hubot)

We could also have an Ansible script for restarting the server and/or webui.

Another idea from @josteinaj is to program our Slackbot to be able to update or restart the test server upon request (only by certain users).

[bertfrees]

The bot idea has been implemented here: https://github.com/nlbdev/snaekobbi-hubot

[bertfrees]

See https://github.com/snaekobbi/system/pull/3