When creating the following bucket notification configuration:
```json
{
    "QueueConfigurations": [
        {
            "Id": "some-id",
            "QueueArn": "arn:aws:sqs:eu-central-1:123456789:my-queue",
            "Events": [
                "s3:ObjectCreated:*"
            ],
            "Filter": {
                "Key": {
                    "FilterRules": [
                        {
                            "Name": "Prefix",
                            "Value": "path/to/folder/"
                        },
                        {
                            "Name": "Suffix",
                            "Value": ".json"
                        }
                    ]
                }
            }
        }
    ]
}
```
and adding some files to S3, I get the following errors from localstack:

```
localstack.services.s3.s3_listener: Unknown filter name: "Prefix"
localstack.services.s3.s3_listener: Unknown filter name: "Suffix"
```

When I change the FilterRule names from "Prefix" to "prefix" and "Suffix" to "suffix", everything works. AWS supports the capitalised name, so this looks like a bug in localstack.
import json
import time
from random import randint
from flask import Flask, jsonify, request, make_response
from localstack.services import generic_proxy
from localstack.utils.aws import aws_stack
from localstack.constants import TEST_AWS_ACCOUNT_ID
from localstack.utils.common import to_str
from localstack.utils.analytics import event_publisher
APP_NAME = 'es_api'
API_PREFIX = '/2015-01-01'
ES_DOMAINS = {}
app = Flask(APP_NAME)
app.url_map.strict_slashes = False
def error_response(error_type, code=400, message='Unknown error.'):