Renamed the local_name_filter attribute to name_regex and made it clear in the
docs that this runs locally and could have a performance impact on a large set
of AMIs returned from AWS.
In cases where the filters provided by AWS against the name of an AMI are not
sufficient, allow adding a "local_name_filter" which is a regex that is used
to filter the AMIs returned by amazon.
This data source allows one to look up the most recent AMI for a specific
set of parameters, much like aws ec2 describe-images in the AWS CLI.
Basically a refresh of hashicorp/terraform#4396, in data source form.
Shawn Silva