Feature #3175: First draft of the SG docs
Feature #3175: Add api docs for security groups
Feature #3175: add ICMP_TYPE to list of valid security groups dialogs
Feature #3175: Update valid SG attrs
Feature #3175: Update upgrade guides
Feature #3175: Document default SG, add update warning
Merge remote-tracking branch 'origin/feature-3175'

Conflicts:
	source/release_notes/release_notes/index.rst
	source/release_notes/release_notes/upgrade_410.rst
	source/release_notes/release_notes/upgrade_48.rst
	source/user/references/cli.rst