Fix #539, parser now supports strings as return. Added a welcome message to the user (SRT). (#543)

* Fix issue #539: parser expanded in order to support strings as return value. logString_type added to types list.
This now should allow to 'project' command to send a wellcome message to the user.

* Fix #539. Added a custom welcome message for the SRT station.

The message reminds the user, whenever the `project` command is issued, to check the status of the telescope in the relative webpage.

* Fix #539, moved the welcomeMessage parameter to DataBlock

Co-authored-by: Andrea Orlati <a.orlati@ira.inaf.it>