more concise path to source uberjar, :artifact-name option

When using lein-init-script with profiles, the `:target-path` provides a more direct path to the generated jars; however, I've found that various different versions of leiningen generate the uberjar in different directories. I added a little mechanism to check in the three places that I've seen uberjars end up [here](https://github.com/jalehman/lein-init-script/commit/9dfd222668e1fe9b15bd3d1c6125cb9b8da1475e#diff-90fbaf6abb9188658d62b0a64dd0c184R87).

Also, I found myself wanting to create multiple init-scripts from the same repository with different names. I added a `:artifact-name` option that renames the copied artifact and scripts.