fix some tests that were failing on Java 8

since they were sensitive to the sort algorithm used (since they
abused the requirements for a sorting predicate)
fix a warning when compiling with Java 8 javac
introduce new nvm.CompilerFlags class

I want to use it in the context of Tortoise, but also it's just
generally cleaner
Merge remote-tracking branch 'origin/master' into modelruns-2.10