Proposal to add a repository to host maven-archetype for SpotBugs plugin project

[KengoTODA]

As @iloveeclipse said in his mail, FindBugs had problem and could not build contributors community.

To build it for SpotBugs, I personally think that it is nice to help developers to develop plugin more active. Because many of core SpotBugs developers are also plugin developers (fb-contrib, find-sec-bug, findbugs-slf4j etc.). Developing original plugin is really useful for developers to make their product stable, and it brings opportunity to read the implementation of SpotBugs too.

Now SpotBugs plugin is not so hard to develop, because it fixed a minor bug which makes product complex, and we also have a module to test with matchers. Then providing project template would help potential contributors to catch up how-to develop plugin, I believe. So I propose to host this project and merge this pull-request to start development as a team.

Note that, of course, documentation is also necessary. Let's improve both of manual and javadoc to get more contribution.
And for now I choose Apache License because I think this is basically nice for Java products, but LGPL v2.1/v3 and GPL v3 are also welcomed if we need to keep consistency with license of SpotBugs itself.

[KengoTODA]

one more note: to pass the build, we need to merge spotbugs/spotbugs#140 because JUnit test needs to load SpotBugs plugin in advance.

[jsotuyod]

This looks amazing! We may want to put the test themselves in a different directory than the one used by the classes to be analyzed in the tests. Maybe a different sourceset?

I personally used a completely different package under src/test/java but never was a huge fan of that solution.

[KengoTODA]

@jsotuyod Please point if I misunderstood what you meant.

Do you mean that it's better to put BadCase.java and GoodCase.java into different package/sourcesets with MyDetectorTest.java?

I prefer putting them into the same package, to group related codes.
But it would be nice to use different source set, to make project clean and well organised.

If we have no understanding mismatch, I will propose another pull request to put BadCase.java and GoodCase.java into new source set such as src/test/cases.

[jsotuyod]

@KengoTODA that is exactly what I meant. Your proposal sounds amazing. Make sure to add proper config to Gradle Eclipse plugin to add that source folder as part of test code.