Small cleanups and release 0.2019pre.1-0co1
A bunch of fixes for which I am too lazy to open a MR for each one:
- Release Canterbury 0.2019pre.1-0co1
- d/rules: Release builds disable -Werror, no need to turn them off explcitly
- d/rules: Revert "Disable tests for now" as they got fixed
- configure.ac: Print the build version in the summary
- d/gbp.conf: Fix spurious escape
- launch_mgr: Fix a -Werror=implicit-fallthrough instance (well, this is part of !4 (closed) already)