Gui 1162 UX review for adding VPC support on the instance launch and launch config wizards

https://eucalyptus.atlassian.net/browse/GUI-1162
https://eucalyptus.atlassian.net/browse/GUI-1228
https://eucalyptus.atlassian.net/browse/GUI-1229
The comment needs to be updated, since we're no longer setting it to "default"