Rename manifest to config

At the same time, this removes the ability to specify config directly
via an option. If that functionality is needed, it can easily
be achieved by writing to a file and specifying that as the config.
Rename group option to target
Fix too many options in struct initializer
Remove --kill option

It's better to stop the containers, so in order to keep Crane
simple, I think it's best to remove the --kill option.
Allow to specify default group
A little ugly; but you can specify -n to specify no-cache.

Signed-off-by: Scott M. Likens <scott@likens.us>
Revert "Remove --kill option"

This reverts commit bbc15bf1bb23b042bc4de88862dd4fc585514d52.

Conflicts:
	cmd.go
	containers.go
Add basic support for pushing images
Format source code
fix installation link to use new Github raw URL