Configurable group type

[neelmitra]

Can the group type be configurable as empty , mock or any name the user chooses ?

In addition the mock service role does not work, we still need to create a seperate role with AWSGreengrassResourceAccessRolePolicy and associate to the account as below.

aws greengrass associate-service-role-to-account --role-arn arn:aws:iam::xxxxxxxxxxxxx:role/GreengrassRole

[brettf]

Focusing this item on "configurable group type" and split the fix role item out to Issue #19.