GUI-337: IAM Policy Generator - Context-specific widgets based on condition keys and operators

Implements context-specific field inputs for EC2 condition keys based on the possible condition values listed at http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-policies-for-amazon-ec2.html#amazon-ec2-keys for https://eucalyptus.atlassian.net/browse/GUI-337

Notes:
- Chosen widget not implemented for select drop-downs due to race conditions--will need to investigate a workaround.
- Need to implement a date picker widget for Date/time related condition operators (e.g. DateGreaterThan).