Sophisticate-ify domain checking, integrate into security module

[michaelpb]

• Should also add in URL reversal to utils/urls.py
• Have it respect the security thing in use

security.py
 51 async def check(typestring, querydata):
 52     if singletons.settings.SECURITY is not None:
 53         checker_class = singletons.settings.load('SECURITY')
 54     else:
 55         checker_class = DummySecurity
 56     checker = checker_class()
 57     url_string = querydata['url'][0]
 58     foreign_res = ForeignResource(url_string)
 59     foreign_res.validate()  # TODO move domain checks into this module
 60     await checker.check(typestring, querydata)