Cfripper

Breaking changes
- `rule_mode` is now `BLOCKING` for all Rules.

Fixed
- `CrossAccountCheckingRule` calling `add_failure_to_result` on `UNDEFINED_` was missing context variable.

Improvements
- `EC2SecurityGroupIngressOpenToWorldRule`, `EC2SecurityGroupMissingEgressRule` and `EC2SecurityGroupOpenToWorldRule` include support for filters.
- `EC2SecurityGroupIngressOpenToWorldRule` and `EC2SecurityGroupOpenToWorldRule` support adding errors for port ranges.
Breaking changes
- `Config.DEFAULT_ALLOWED_WORLD_OPEN_PORTS` type changes to `List[int]`
- Rename `SecurityGroupIngressOpenToWorldRule` to `EC2SecurityGroupIngressOpenToWorldRule`
- Rename `SecurityGroupMissingEgressRule` to `EC2SecurityGroupMissingEgressRule`
- Rename `SecurityGroupOpenToWorldRule` to `EC2SecurityGroupOpenToWorldRule`
- Improved message for users when failing the `SecurityGroupOpenToWorldRule` and `SecurityGroupIngressOpenToWorldRule` rules.
- Improved documentation for the above rules, including styling fixes which have now been tested.

Improvements
- Improved message for users when failing the `SecurityGroupOpenToWorldRule` and `SecurityGroupIngressOpenToWorldRule` rules.
- Improved documentation for the above rules, including styling fixes which have now been tested.

Improvements
- Add `exists` and `empty` functions to filters
- Add `param_resolver` to filters to evaluate just necessary params
Fixed
- Add protection when a filter is evaluated to catch the exception and continue

Improvements
- `CrossAccountCheckingRule`, `CrossAccountTrustRule`, `S3CrossAccountTrustRule` and `KMSKeyCrossAccountTrustRule` include support for filters.
Breaking changes
- `CrossAccountCheckingRule` now includes the invoke method. Statements of PolicyDocument are now analysed using `RESOURCE_TYPE` and `PROPERTY_WITH_POLICYDOCUMENT` class variables.