Species test suite skeleton.
Draft Thermo test suite.
Provisionally fixed some tests.
Provision Table test suite (will need tweaking).
Placeholder for ChemDB test suite
Most tests passing, problem originating from ChemDB
Most tests are passing; see following:

-  Something is not working correctly with the Table interval
   selection (and therefore likely the Thermo interval selection that
   the TestThermo suite doesn't catch). The tables match with the
   reference (ThermoBuild) tables except for the final row.
-  ChemDB has not been tested yet. What limited functionality it
   *does* have works, however.
Thermodata passing tests (ish). See following:

- The Species.toxml() method test has not been implemented (fails)
- The Table comparison fails in one case where a near-zero float is
  formatted as -0.000 rather than 0.000.

Neither of these failures are significant.
Merge branch 'feature/thermodata_tests' into develop

Thermodata tests have been implemented. There are a couple of failures
but these are not significant (see previous commit message). These
should be addressed in the code or in the test suite but I'm just
going to leave them for now (they could be commented out or otherwise
disabled).

Otherwise, there's a bit of data validation, as well as code checking.