Maven Plugin should output `.nondex` directory in the project's build output by default

[bdemers]

The maven plugin currently litters the project tree with a .nondex fold in each module of a multi-module project.

The default output directory should be the project's build directory (target by default).

[kaiyaok2]

.nondex folder is where NonDex stores temporary files for the debug mojo (if one wants a stack trace of the invocation of an under-determined Java API). We have a clean mojo to remove those: for example, with NonDex 2.1.1, run:
mvn edu.illinois:nondex-maven-plugin:2.1.1:clean

[bdemers]

@kaiyaok2 right! And that's a good idea, but littering a project's source directory is not typical behavior for a Maven plugin; any generated content should go into the project build output-dir.