…se on nix systems.

- Completely reworked Maven plugin (should fix many of previous issues
and inconsistencies between main and test builds).

- Added `classesDirectory`, `debug`, `fallback`, `verbose`, `sharedLibrary`,
`configurationFileDirectories`, `excludeConfig` and `jvmArgs` properties in
order to match those present in the Gradle plugin.

- `useArgFile` is now set to true by default only on Windows

- Added `excludeConfig` configuration option that allows skipping of
configuration files that are present in classpath `jar` s.