added support for JSON format, fixed typos, took care of a couple issues

[obpedro]

We recently moved from using syslog to the [JSON format events (https://help.deepsecurity.trendmicro.com/aws/event-sns-json.html) so we went ahead and updated the TA internally to add support to the new format, and thought we could contribute the updates back to the source repo. :)

I did the best I could to map fields to the CIM data models, however for two of the event types (App Control and Web Reputation) I relied on documentation to do the mapping since we don't have those modules and therefore I didn't have events in Splunk to look at.

One thing is we went with indexed_extractions = json as we've had success with that setting in json events (and it is what the AWS TA uses, so we decided to go with that).

With regards to the dashboards, I simplified some things a bit, mainly using the CIM fields as much as possible to allow them to be agnostic to the JSON or syslog sourcetypes. A possible improvement is to use eventtypes instead of sourcetypes to make the search string shorter, but I decided to leave it alone for now.

I went ahead and added the fix for issue #8 and updated the deepsecurity-cefcustom transform.

Please let me know if you have any questions!

Thanks,
Pedro