recipetool: create: extract name of package from a repository

recipetool: create: extract name of package from a repository

For git repositories in the absence of any other indicator, it's not an
unreasonable assumption that the name of the repository is the name of
the software package it contains, so use that as PN if we don't have
anything else.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>