Fixed GUI tab order. Refs #7637.
Added validation to GUI. Refs #7637.

- Removed useless label from GUI.
- Added relevant label to inform user of the catalog they're logged into. The label is also used for error message if they are not logged into ICAT rather than re-opening a login dialog.
- Enabled header to calendar.
Hide elements on GUI. Refs #7637.

- I have opted to hide elements that related to functionality that will not make it into this release, such as paging and multiple facility login.
Minor UX improvement during search. Refs #7637.
Hide old ICAT GUI menu items. Refs #7637.

- I have hidden these rather than removal as this will be done in another ticket along with the older ICAT GUI classes/files.
Create new icat GUI when menu clicked. Refs #7637.

- If I had not logged in and then clicked `Search` I would get error messages (great). However, if I closed the ICAT GUI and logged in and clicked `Search` again then I would get the previous GUI. This is no longer the case.
- Ensures only one ICAT GUI can exist.
Merge branch 'feature/7637_improve_icat_gui' into develop