AWS::ElastiCache::ParameterGroup - CacheParameterGroupName

## 1. Title
New attribute
AWS::ElastiCache::ParameterGroup-**CacheParameterGroupName**

## 2. Scope of request

1) AWS::ElastiCache::ParameterGroup should allow initializing with a user-inputted CacheParameterGroupName.
2) CacheParameterGroupName should be a callable attribute.

**Why:**
1) CacheParameterGroupName is what shows in AWS Console.
2) AWS::ElastiCache::CacheCluster has the optional init parameter CacheParameterGroupName. It is difficult to reference to a ParameterGroup due to it not having a callable name attribute. (Workaround is that Ref resolves to it).

## 5. Helpful Links to speed up research and evaluation

ElastiCache API supports this:
https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_CacheParameterGroup.html

CFN doesn't:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-elasticache-parameter-group.html

CacheCluster requires it:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-elasticache-cache-cluster.html

CDK requires CFN to implement this first:
https://github.com/aws/aws-cdk/issues/8180

## 6. Category (required)
3. DB (RDS, DynamoDB...)