Hability to execute java ('exec:java') without requiring a maven project, and allow dependency resolution

exec:java currently needs a maven project (pom.xml) to load the project dependencies in order to find the main class (and its dependencies). It would be nice to run a exec:java without this requirement, so the goal could resolve dependencies passed by command line arguments and run the main method (also passed by command line argument).

exec:java goal could be altered, or a new goal (say, exec:anyjava) could be created so the impact on exec:java would be minimum. Also, a mechanism similar to dependency:get would be needed to resolve the dependencies that are passed by command line.

I have some working code that I'll send in a PR soon.

Start by reading the exec:java goal and the linked Maven dependency:get mechanism. Determine how a goal can run without pom.xml while resolving command-line dependencies and accepting the main method as an argument; done means a standalone invocation can execute the requested Java program and its dependencies without unnecessarily changing existing exec:java behavior.