Make Like Reactor Mode

Add a commandline option to enable maven to expand the reactor scope to find projects that are dependencies
of the projects currently in the reactor, and add them.

Currently only the current project and child projects are included in the reactor search. I'm proposing
to add a commandline switch that lets maven check parent directories to find the root of the project tree,
and then do a normal reactor scan, only adding projects that would normally not be added if they're needed
as dependencies of the projects that would normally be built.

Here's a sample project tree:

• root
  • p1
    • c1 (depends on p2)
  • p2 (depends on c2)
  • p3
    • c2

And a sample algorithm:

• When building c1, the reactor would contain [c1].

• Maven would check p1, then root, etc, using the <parent> tags (without the versions!)
  to see if the project is still in the current reactor.

• It would then create a second list of projects (reactor2) containing ALL projects, using the newly discovered root: [root, p1, c2, p2].

• remove all projects from reactor2 contained in reactor: reactor2 = [root, p1, p2]

• resolve all direct dependencies for all projects in reactor in reactor2 and add them to reactor, taking versions into account: reactor = [p2, c1]

• repeat previous step until all projects have their dependencies resolved from reactor 2. first iteration would yield reactor = [c2, p2, c1],
  next iteration would stop since c1 doesn't have any dependencies present in reactor2.

This would ensure that when some local project's sources have changed, they'll be incorporated
in the build, regardless of where you build. So you don't have to do a reactor build each time you change more
than 1 project, and you don't have to remember which projects you changed and build them in the correct order
yourself, manually.