Cloudwanderer

- Dispense with wrapper methods and instead subclass the boto3 resource factory so we can create new methods directly on the ServiceResource objects.
- Added Gremlin GraphDB storage connector

- Added `requiresLoadForFullMetadata` to service mappings. Allows resources like Regional WebACLs to declare that they get impoverished data from their list operation and need `resource.load()` called to fetch all info.
- Added support for services which have both regional *and* global resources
- Moved get_and_cleanup_actions from CloudWandererBoto3Resource to ResourceMap
- Added Resource Filtering options to flexibly filter out resources you're not interested in.

New Resources
- Added ec2 nat gateways
- Added ec2 egress only internet gateways
- Added ec2 vpn gateways
- Added ec2 vpn customer gateways
- Added ec2 vpn connections
- Added wafv2 regional web acls

New Resources
- Added ec2 vpc endpoints support
- Added ec2 vpc endpoint services support
- Added ec2 elastic IP support
- Added elbv2 target group support
- Added elbv2 load balancer support

- Fixed memory leak due where decorating with `lru_cache` caused old objects' caches not to be garbage collected.

- Allow subresources in `write_resource`
- Escaped URNs with forward slashes
- Provided way to explicitly specify base resources with multiple identifiers as a base resource.
- URNs are now made up of unlimited resource ids aka `resource_id_parts`.
- URNs now have a `resource_id_parts_parsed` which will attempt to convert non-string id parts into their appropriate type (fixing a bug preventing us from getting lambda layer versions from URN)
- Added Boto3 resource/service definitions as part of service maps as the first steps to making service maps wrap Boto3 definitions fully.
- Resources and subresources no longer have to have specific numbers of identifiers, fixing a bug that caused Cloudwatch Metrics to be misidentified as a subresource.
- Service and Resource maps now have a `boto3_definition` attribute which is the start of the work to have service maps properly superordinate to Boto3 definitions.
- `resource_summary` now includes more detailed information about subresources
- `CloudWandererResource` now generates `parent_urn` property from service mapping data using its news `boto3_definition` property.

Resources

- Added AutoScalingGroup fixing [123](https://github.com/CloudWanderer-io/CloudWanderer/issues/123)
- Added load operation for lambda layer versions

- Added `lambda` `layer` resource type.
- Added `lambda` `layer_version` subresource type.
- Added `py.typed` for PEP561 support.
- Added documentation on writing custom resource definitions.
- Fixed bug where resources could not build URNs if they had non-string ID components.