Cfripper

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.

Improvements
- Add new `RuleConfig`, allows to overwrite the default behaviour of the rule changing rule mode and risk value.
- Add new `Filter`, allows setting custom rule configuration to matching coincidences.
- New RuleModes supported: `RuleMode.DISABLED` and `RuleMode.WHITELISTED`.
Breaking changes
- Class variables `Rule.RULE_MODE` and `Rule.RISK_VALUE` should be changed to use properties `rule_mode` and `risk_value`. These properties take in consideration the custom config that might be applied.
- If rule mode is `DISABLED` or `WHITELISTED`; methods `add_failure_to_result` and `add_warning_to_result` will have no effect.
- `add_failure_to_result` and `add_warning_to_result` accepts a new optional parameter named `context`. This variable is going to be evaluated by filters defined in the custom config.