Update manifest to set up virtualenv with default local requirements, li...

...ke what is done in icommons_tools.  Move LTI_OAUTH_CREDENTIALS setting into base, since that's what needs to be done across environments anyway.  Include HU common libraries like icommon-ui, icommons-common, and django-auth-lti by version or branch depending on environment as opposed to always including what's in master.  This is also akin to what's done in icommons_tools.