Multiple improvements.

• Fixed artefact deployment for detached repos.
• Added DB caching between builds.
• Added watchdog error checker to Behat.
• Added app:drush command.
• Added parallel code syntax checker.
• Added PHP compatibility sniff.

Simplified CI

8.x-0.7

[#28] Fixed generated settings being included into artefact.

Updated artefact version.

8.x-0.5

Updated artefact building script to the latest version.

Docker!

Moved local and CI to docker

7.x-0.4

Updated CI config. (#25)

7.x-0.3

Backporting from 8.x branch.

8.x-0.3

[#21] Disabled apt update.