Compilation no longer enforces unit test runs

In passing, eliminate a few other warnings too.

Now each unit test subdirectory has an identical copy of main.cpp,
and a file testlist.h that consists of #include's of all other .h
files in the subdirectory.
For the time being, the files testlist.h are not automatically
updated, but there is a script dev-tools/code-tools/update-gtestlist.py
that can be run when needed.

Top-level routines moved from Fit/Suite to Core/Fitting.
Some base classes and utilities moved from Core to Fit/Utils. This requires more thought.

merged unit test directories P and Q into Numeric; moved file from S to 1; made WRAP_GTEST more flexible

2. Tests for AttLimits, FitParameter, FitParameterLinked