Added opt-out of the actual awseb deploy

Completely and utterly untested code.

Added an opt-out from awseb checkbox.
If checked, it will skip the "updateEnvironment" call.
The addition leaves current settings and behaviour untouched as the default state (unchecked) will not change anything.

This is the first time I've ever written anything in a Jenkins plugin so I'm not sure if the checkbox handling in the builder (boolean) will work.