Better test assertions for exceptions.

Google Test assertions (ASSERT|EXPECT)(_NO)?_THROW only print
"Actual: it throws." or similar when the assertion fails.  Added
Gromacs-specific exception assertions to improve output in these cases.
The new assertions have a _GMX suffix, and are used the same as the
Google Test ones.

The only real code changes are in src/testutils/testasserts.h and in
src/gromacs/utility/exceptions.*; all the other changes are mechanical
replacement of existing macros.

Change-Id: Iadcf08a0148fdcb6228e0abccea89c33d817a018