Test logging strings

[matteobecchi]

We should add tests for the logging messages.

Not implemented yet because:

• Maybe we want to change their format one we start using it
• The test is made a bit hard because strings contain logging date and time, which are never the same, and thus has to be removed from the comparison.

[matteobecchi]

Moreover, write docs for the logging module, and add the software version to the logged information.

[matteobecchi]

There are a lot of tests on the logger after PR #124 . I think this can be closed.