Jenkins integration

[beauof]

• set up Jenkins build server
• weekly testing of cbm-software/iron repo (devel branch) using keytests target
• allow users to trigger tests on demand
• modify python script with matplotlib to also work without X server
• modify cmgui scripts to work without X server
• use cbm-software/iron-tests for pull-requests and nightly tests of cbm-software/iron
• automated tests of pull-requests
• automated merge of successful test of pull-request

[maierbn]

• modify python script with matplotlib to also work without X server

edit by @beauof: Included item in list above.