pycadf documentation

add basic documentation on CADF spec.

Closes-Bug: #1279951
Change-Id: Ie1703d9b5109d8275377857e5362e3b09385f647
Implements: blueprint document-pycadf
add OpenStack Foundation as author

add OpenStack Foundation as author

Change-Id: Iac1b743fa4c0d0ead2badaee5f36451e91465bf0