Migrate mass_spec cmake test project into qmake test project with googletests

[PMSeitzer]

Currently, there are a series of maven-associated tests in https://github.com/calico/mass_spec/tree/master/lib/cpp/mzkit/libmzkit

This is OK, but given that the majority of the code is maven_core, it would probably be better to put these test classes directly into the maven as a subrepository (similar to peakdetector and maven_core).

At present, this is a cmake project which also contains various executables for various other tools. It might be nice to restructure everything into qmake, or at least separate out individual executables into separate qmake projects. Alternatively, everything could be ported to qmake - though this has the disadvantage of being tougher to test with other IDEs/frameworks.

Ultimately, this should all probably be set up in such a way as to carry out automatic unit testing on every build. This had been set up for some DIMS work, but has since fallen by the wayside a bit.

[PMSeitzer]

The module could be called maven_tests.

[PMSeitzer]

http://www.robert-puskas.info/2019/09/lod-setting-up-project-with-unit-testing-qt-creator-proper.html

[PMSeitzer]

Note googletests github: https://github.com/google/googletest

[PMSeitzer]

As a part of this work, explore introducing qmake unit tests, e.g. through qt tutorial: See https://doc.qt.io/qt-5/qttestlib-tutorial1-example.html

[PMSeitzer]

A migration might not be a great choice, but if a test is desired that uses qt-specific components, this might be one option.

[PMSeitzer]

A rudimentary testing module, maven_tests, has been developed. Closing this issue.