Merge test2 and runtests2 and modify their signatures

[apjanke]

This follows up discussion in #42 (comment)

@cbm755 things runtests2 and test2 should converge to a single function with different operation modes, to present a unified interface to the end user.

Consider doing this, and discuss what the resulting interface would look like.

[apjanke]

So, I think this probably looks like folding all the functionality into runtests2, eliminating test2, and providing additional options to control the verbosity of both the console and log file outputs (independently), and an option to not produce a log file at all. Because, I think, the difference between test and runtests is that test runs tests on a single file, and displays verbose output to the command window but does not produce a log file, while runtests tests one or more files, displays more concise output to the command window, and produces a log file with the detailed log output.