Create a DynamoDb table to store risk assessment results

[brianok77]

This table will have the following features:
Partition Key: {device guid}
Sort Key: {risk assessment key}#{assessment timestamp -- YYYYmmdd"T"hhMMss format}

It should also have 3 other columns:
Score
Risk Assessment Measure Key
Assessment Timestamp

Duplicating the subkeys of the sort key as columns will allow us to leverage them in secondary indexes later.