Add support for more actions to be guessed

#22 introduced a feature to guess actions that are similar to an existing policy. It currently doesn't support all actions.

Here's things I currently know are missing (comment if you find more):

* [ ] KMS: `Encrypt`, `Decrypt`, `GenerateDataKey`, ...
* [ ] ECR: `BatchDeleteImage`, `BatchGetImage`, ...
* [ ] `*Deregister*`
* [ ] `*Modify*`
* [ ] `*Remove*`
* [ ] API Gateway: (`DELETE`, `GET`, `HEAD`, `OPTIONS`, `PATCH`, `POST`, `PUT`)

How to do this?

* Add a test case in [`tests/iam/action_test.py`](https://github.com/flosell/trailscraper/blob/master/tests/iam/action_test.py)
* Modify [`trailscraper/iam.py`](https://github.com/flosell/trailscraper/blob/master/trailscraper/iam.py) (in the simplest cases, this is just adding something to `BASE_ACTION_PREFIXES`)