Add the ability to specify "." for a project name
Add the ability to specify "." for a project name

This uses the current directory and gets the project name out of git and
then maps that to the project name(s).  In the case of no mapping, it
dies with a message.

Included more changes per review comments by David and Richard.

BUG=chromium-os:20338
TEST=cd src/platform/vpd; cros-workon start .

Change-Id: I6d31d63fe515558286623c177c23fa50a0977b9b
Reviewed-on: http://gerrit.chromium.org/gerrit/7577
Reviewed-by: Richard Barnette <9e7d66387742bf40b0d2548ef2b93e7c522ca0eb@chromium.org>
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Reviewed-by: Terry Lambert <f31fd7e0e83d662934f80cc9a2fd8f7385851082@chromium.org>
Tested-by: Terry Lambert <f31fd7e0e83d662934f80cc9a2fd8f7385851082@chromium.org>

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