Removed old ICAT interface classes. Refs #8274.

- Removed relevant classes from cmake list.
Removed advancedSearch from application window. Refs #8274.
Removed MyDataSearch from application window. Refs #8274.
Removed ICatSearch from application window. Refs #8274.
Renamed ICatHelper class. Refs #8274.
Renamed ICatSearch class. Refs #8274.

- Renamed `Login` `search`, and `logout` variables in `ApplicationWindow.cpp` to be ICAT independant.
- Renamed relevant interface class to match related class name.
- Updated CMakeLists.
Remove unused ICAT methods MantidUI & ApplicationWindow. Refs #8274.
Merge remote-tracking branch 'origin/master' into feature/8274_icat_remove_old_gui. Refs #8274.

Conflicts:
	Code/Mantid/MantidQt/MantidWidgets/src/CatalogHelper.cpp
	Code/Mantid/MantidQt/MantidWidgets/src/CatalogSearch.cpp
Removed deleted files from CMakeList. Refs #8274.
Removed unused logout method from MantidUi. Refs #8274.
Make use of asynchronous method. Refs #8274.
Merge remote-tracking branch 'origin/feature/8274_icat_remove_old_gui'
Merge remote-tracking branch 'origin/master' into feature/8244_icat_date_selector_issues. Refs #8244.

Conflicts:
	Code/Mantid/MantidQt/MantidWidgets/src/CatalogSearch.cpp