* provider/aws: Add support for aws_ssm_maintenance_window
Fixes: #14027
```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSSSMMaintenanceWindow_basic'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/29 13:38:19 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSSSMMaintenanceWindow_basic -timeout 120m
=== RUN TestAccAWSSSMMaintenanceWindow_basic
--- PASS: TestAccAWSSSMMaintenanceWindow_basic (51.69s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 51.711s
```
* provider/aws: Add documentation for aws_ssm_maintenance_window
* provider/aws: Add support for aws_ssm_maintenance_window_target
```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSSSMMaintenanceWindowTarget'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/29 16:38:22 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSSSMMaintenanceWindowTarget -timeout 120m
=== RUN TestAccAWSSSMMaintenanceWindowTarget_basic
--- PASS: TestAccAWSSSMMaintenanceWindowTarget_basic (34.68s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 34.701s
```
* provider/aws: Adding the documentation for aws_ssm_maintenance_window_target
* provider/aws: Add support for aws_ssm_maintenance_window_task
* provider/aws: Documentation for aws_ssm_maintenance_window_task