Bugfix/add ci case with ffpe trap

• Add a Debug CI case which forces initialisation of values and watches for invalid operations

• Turn on flags

Tries to check for places where we use uninitialised variables.

Requires PR #499, PR #500, PR #501, PR #502, PR #503, PR #504, PR #505, PR #506 and utils PR 107 to pass

PR #508 also need if the -finit-integer value is changed from negative to positive.

Note the floating point initialisation and traps are not perfect. With gfortran these options to do not impact allocatable arrays and indeed we know that PR #475 fixes a known use of uninitialised data which is not currently fixed in the code in this branch but is not caught. We have also tested with intel which can initialise allocatable arrays to NaN but cannot initialised derived type components. This caught an extra bug fixed in PR #512