livestatus counters: clean + share livestatus.counters + use lock.
LiveStatus tests: Skip cache tests for now.
Enh: For easier dev, tests, debug : allow to directly execute shinken in "dev" mode.

By dev mode I mean :
To be able to clone the repository as a non-privileged user in any directory,
and then to directly execute the daemons or the tests.
This without nearly any other step required,
it depends if you have the dependencies available or not.

The daemons will use the "var" directory as working directory.

The less dependencies/requirements you have for doing anything : the better.