(May re-instate old ICAT code as a second, backup searcher, and also need to create one for HFIR instruments with run numbers.)

I should probably get round to working out how to call it locally...

Included moving a TS_ASSERT out of a destructor in a mock object, which would have been harmless.  I couldn't use noexcept(false) as a workaround because of the parent destructor.  The resulting code is much messier as I have to keep ahold of the mock object and call the assert in each of the tests... :(

I haven't added a PrecompiledHeader.h yet.  I'd be open to adding one in this PR if a reviewer thought it was important enough.