Removed unnecessary try/catch from catalog algors. Refs #8445.

- The try/catch is no longer needed as we should not use these algorithms as a means of checking whether a user is logged in. Instead we have enabled/disabled the appropriate menus in another ticket.
Removed methods that are no longer needed. Refs #8445.
Tidy algorithms. Refs #8445.

- Used auto when possible for cleaner code.
- As most of the algorithms only make use of the catalog to invoke a specific method I now do this directly rather than in two steps.
Merge remote-tracking branch 'origin/master' into feature/8445_icat_refactor_algorithms. Refs #8445

Conflicts:
	Code/Mantid/Framework/ICat/src/CatalogLogin.cpp
	Code/Mantid/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/CatalogHelper.h
Merge remote-tracking branch 'origin/feature/8445_icat_refactor_algorithms'