GUI-1291
updated chosen widget to take <enter> as 'take this value for an option'. Use it on the create IS image page.
GUI-1291
another tweak to chosen to dismiss list after new value added
GUI-1291
added 'create_with_enter' for other chosen widgets that support new values
Merge pull request #1010 from eucalyptus/GUI-1291

GUI-1291 updated chosen widget to take <enter> as 'take this value for an option'.