Correct a few minor issues in PR OPM/opm-core#254

Pull request OPM/opm-core#254 is generally very good and highly welcome, but there are a few minor coding issues that would be better fixed before merging it into `master` of OPM/opm-core.

This pull request addresses those issues.  In particular,

* It assumes (and enforces) a `FIELD` unit convention on the test data, `testFluid.DATA`
* It re-indents `CMakeLists_files.txt` using `<tab>`s rather than `<space>`s
* It replaces several variably sized arrays with the equivalent `std::vector<>`s