Add support for BIG-IP 13.0.x
Add support for BIG-IP 13.0.x

Issues:
Fixes #206

Problem:
We need to document our support for 13.0.x BIG-IP versions.

Analysis:
Added 13.0.x support and removed 12.0.x

Tests:

jputrino/f5-openstack-docs,F5Networks/f5-openstack-docs