ci: Support for pylint and yamllint

ci: Support for pylint and yamllint

A support for pylint and yamllint checks was introduced.
Checks can be executed manually by invocation of ./check
script (see script usage for more details). Automatic lint
checks were integrated info VERIFY and MERGE job bodies.

TODO:
Improve pylint ratings of python code. Some issues can
be fixed in python files or by relaxing pylint settings.
However dependencies on ONAP includes can't be easily fixed.
Thus pylint checks should be set as non-blocking at the beginning.

Change-Id: I82a6a266b8003ae5d70f4f2a88ecc96817b97ac0
Signed-off-by: Martin Klozik <martin.klozik@tieto.com>