Make an explicit 'load content' step in bootstrapping.

[smn]

This addresses @SteveBarnett's concerns around the current bootstrapping tool requiring both a name and a git repo url.

[smn]

[smn]

@SteveBarnett & @miltontony ready for review.

Based on @SteveBarnett 's suggestions I've refactored things a bit. I think it's a mistake to only use the URL because 'creating the app' and 'loading content' are essentially two different things in Universal Core (by design).

The current command line tool usage is:

$ springboard startapp foo
$ cd foo
$ springboard import git://your/git/repo.git
$ pserve development.ini

[SteveBarnett]

@smn Nice! I like this new version. 👍