Added a type file for the new ISO type.
Added the beginnings of an ISO Importer.
Use the entry point system to announce the ISO importer.
Got the beginnings of an ISO Distributor, and a demo script.
A very basic working importer, but more needs to be done.

There are many TODOs still, and no unit tests.
Have a nearly working distributor, though very basic.
We now have a very basic working distributor.
Merge branch 'pulp-2.0' into rbarlow_iso_importer_distributor
Test for the existence of symlinks before creating them during Publish.

Also, try unsuccessfully to stop Grinder from downloading files multiple
times.
Small change to my demo script.
Add some simple validation for the ISO distributor config.
Merge branch 'pulp-2.0' into rbarlow_iso_importer_distributor
Add some basic configuration validation to the ISO importer.
We now have the ability to avoid downloading files that we already have.
Added some docblocks and adjusted parameter names and types.
Added a partial implementation of SHA256 and size validation for
downloads.
Add support for checksum validation.
Added the beginnings of SSL support.
Merge branch 'pulp-2.0' into rbarlow_iso_importer_distributor

Conflicts:
	.gitignore
	pulp_rpm/src/pulp_rpm/common/constants.py
Try to use CA certs, but they don't quite function correctly yet for
some reason.