Add Maven nature and build instructions so as to test BuildHive

Status: Local Maven build works from Eclipse, but I have no idea
whatsoever if it will work on BuildHive. I have next to zero Maven
knowledge, so I will just try.
Remove commented-out garbage, add line feed at EOF
Add "attachToBuild" property to one-jar Maven configuration

Hopefully this helps to get the one-jar artifact deployed to the private
Maven repo at CloudBees.
Merge branch 'master' into maven_build
Merge branch 'master' into maven_build
.gitignore: ignore "/bin" leftovers after branch switch
Merge branch 'master' into maven_build
Merge branch 'master' into maven_build
Merge branch 'master' into maven_build