Added configuration option 'user', which if defined and not empty will add a username to the path of a measurement, right between the root directory and the datestamped
directory. The option can also be overridden by specifying a new argument called user that has been added to Data.create_file(), and a Parspace object will do this if it has a
property named user with any other value than None.
Also adapted the qtlab-starting shell scripts for *nix so they use python2 on a system where both Python 2 and Python 3 are installed.
Finally I added a missing import statement to the testParspace measurement script.
Added a GUI element to set the user. Currently it's just functioning as a text field, but in the future it should also have a dropdown menu with some common users as well as
functionality to add a common user by pressing enter. Also, the last
user from a previous session is remembered but this is not yet reflected
in the GUI initialisation.