GUI-337: IAM Policy Generator - Selective display of operators for conditions

Implements the following for https://eucalyptus.atlassian.net/browse/GUI-337 …

- Only display operators that are appropriate for the selected condition key in a policy statement, per AWS docs at http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-policies-for-amazon-ec2.html#amazon-ec2-keys (for EC2-specific keys) and http://docs.aws.amazon.com/IAM/latest/UserGuide/AccessPolicyLanguage_ElementDescriptions.html#AvailableKeys (for AWS-wide keys)