Refs #9457 - Add SANS2DTUBES() to the ISISCommandInterface.
Refs #9457 - Add temp SANS2DTUBES option to GUI.

Replaced InstrumentSelector widget with plain QComboBox, as it was the
easiest way to get SANS2DTUBES in the dropdown.

Some nasty hacks to accomodate the new option.

Everything in this commit should be reversed upon completion of #9367.
Merge remote-tracking branch 'origin/bugfix/9457_temp_workaround_for_sans2dtubes_idf'