Support for multiple test summary Plists/destinations

[lyricsboy]

Related to #4.

This adds:

• support for overriding the path parameter via the Fastfile (https://github.com/KrauseFx/trainer/commit/0724404b5a3b7ffc580f88e72c8b7b08c7168e1b)
• properties to the JUnit XML output that help distinguish run destinations
• a package attribute based on the run destination's name + OS Version

It changes:

• the way that TestSummaries.plist files are searched for. It uses a recursive path spec to find any files ending in _TestSummaries.plist. This avoids creating output based on the duplicative TestSummaries.plist file in the root of the result bundle.

[KrauseFx]

Cool, thanks 👍 Do you think you can test this in production and ensure this doesn't break anything existing, and works with the new setup?

[lyricsboy]

I can't guarantee my availability to test it in production but I'll try. @CraigLn is this something you can test?

[sudheer549]

Has any one tried this commit, needed this one as need to run multiple devices

[BlackWolf]

Any advice on what's preventing this from being merged? This would be really valuable for us :-)

[slk9]

Any plans to merge this PR? It is 2 years old and I don't see why it is not in yet when everyone including me :) needs it. Time fly so, Xcode 11 supports test configurations which another test suite distinguish information needed to be added to JUnit.xml