When copying script/launchjar to new project, use old launch jar

Activator home may not match our own version, so we glob the
launch jar if we have to (first checking for an exact match,
just for efficiency and in case there are multiple).

Fixes #555
Don't copy scripts to new project without a launchjar

If for some reason we can't find the launch jar, don't
copy the scripts, since they won't work by themselves.
Merge pull request #571 from typesafehub/wip/havocp-clone-old-launcher

Fix cloning launch jar from old activator home