Port the dogfood feature from Gradle to Maven

[nedtwigg]

It would be handy if you could contribute to any Eclipse project by doing mvn equo-ide:launch and get an IDE setup for that project.

It would also be handy if you could build a new IDE plugin, and then add it to your launched IDE as you build it for easy dogfooding. This is possible right now in our Gradle plugin like so

equoIde {
  jdt()
  dogfood() // compile this project, then add it to the launched IDE

This feature in Gradle was implemented like so

• Make it easy to dogfood IDE plugins #143

It would be great to support this for the maven plugin as well.