CI to harden the code

[glpatcern]

Similarly to the Reva repo, we should add a CI to at least:

• pylint the code
• run the unit tests against a local filesystem
• run the unit tests with the cs3 flavor against a live Reva daemon
• run the WOPI validator test suite against a live WOPI server connected to a live Reva daemon

This should be activated as usual to any PR against the master branch - as well as any direct commit to master.

[glpatcern]

The "easy" standalone part was integrated successfully. Keeping the issue open for the test against a live Reva daemon.

[glpatcern]

As discussed with @javfg, we should use a custom GitHub runner similarly to what @vascoguita has setup for Reva, such that a live Reva daemon is in place and two containers are created: the wopiserver one and the WOPI validator one. TBC.

[micbar]

the ocis project has the WOPI Validator running in the CI

This is an example https://drone.owncloud.com/owncloud/ocis/22470/46/9