Allow specifying what package statuses should be searched for.
By default search only for Pending and Published, unless a specific
version number is being searched for.
The UCA source pkg class was its own specific class, but with the
addition of the generic PPA source pkg class, the UCA class is just
a specific case of PPA. Changing it to a subclass of the PPA class
simplifies code.
Change dsc verification to fail only if the public key was available, but
signature verification failed. If no public key is available for the dsc,
print warning only. (LP: #1700846)
Also add pull-* parameter --no-verify-signature to manually prevent failure
when signature verification fails.
rename only with no content changes, so next commit shows code
changes converting script pull-pkg to module pullpkg.py
This also changes the file mode from 755 to 644, since we're changing
an executable script into a module.
