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
Lines 394-398 can be simplified to the following…

```
associate_public_ip_address_param = self.request.params.get('associate_public_ip_address')
associate_public_ip_address = True if associate_public_ip_address_param == 'true' else False
```
or even…
```
associate_public_ip_address_param = self.request.params.get('associate_public_ip_address')
associate_public_ip_address = associate_public_ip_address_param == 'true'
```
…although the former is probably more readable IMO