This starts to address #2965. I have pulled the ant integration out of JRuby into a gem but it does not yet pull down Ant itself.

A few notes:

• License is EPL 2
• File structure has been updated to conform to namespacing norms (most stuff under rake/ant).
• I had to include Rake::DSL into the toplevel of rake/ant/ant in order for bare calls to "tasks" and other top-level Rake DSL methods to work. There may be a cleaner way to make this work without polluting toplevel.
• I'm not sure how best to pull down Ant. I assume it would be something in jar-dependencies but need help/advice from @mkristian here.

With the current pulled-out gem, we can build as normal and still run rake builds that (unfortunately) still depend on ant.