usd-clone: add usd-clone simple wrapper for cloning
This just adds a wrapper that knows urls to keep typing down.
It tries to find the launchpad user, and prompts if it can't find one.
If provided with a user name via prompt, it will offer to store
that username in git config by configuring an 'lp:' remote.
It clones from the importer location, and sets up the following remotes:
importer git://git.launchpad.net/~usd-import-team/ubuntu/+source/<pkg>
lpusd git://git.launchpad.net/~ubuntu-server-dev/ubuntu/+source/<pkg>
<user> git+ssh://<user@>git.launchpad.net/~<user>/ubuntu/+source/<pkg>
Where '<user>' is launchpad user.
It then sets a local branch 'master' to track importer/ubuntu/devel,
and checks that branch out.
There were a few bugs in the override logic, because of the time of
interpretation of a string like './usd-import' -- '.' is changed by
the chdirs in the script itself.
After discussions with Barry Warsaw on IRC (#ubuntu-devel), reorganize
the importer into a proper package (usd) and place the relevant override
files and patches in that package. This will allow us to use
pkg_resources to get the absolute path to the resource.
