Add special case detection of Gradle environment

[rnorth]

…and always enable ANSI escape codes

[rnorth]

FYI @bsideup - this adds a workaround to force ANSI colour codes on when running under Gradle.

Like the Maven/IDEA detection, it's a bit hacky and based on what's available (not much). Still, this is the only option I see. I think the previous (pre 'regression') behaviour in TC master might have been a bug - it was using ANSI color codes when it shouldn't have been.

With this new change, we'll have forced ANSI codes on for Gradle builds too, though, and the desirable bits of behaviour should be back.