2.0 Refactor

[timkelty]

Enough has changed here, that this would have to be 2.0.

Here's a summary:

• Following the pattern of other Yii drivers like Redis, I separated all the Dynamo-specific stuff to it's own Connection component.
• AWS_REGION is now automatically used if present
• keyPrefix has been replaced with formatKey, which will allow more flexibility and is compatible with compound keys
• Adding a default ttl is now possible via ttlAttribute and ttl.
• The SDK's Marshaler is used, and is exposed as a property for use.
• consistentRead is exposed an option (lifted from https://github.com/aws/aws-sdk-php/blob/3d0d24d9dad824ea4344cfc711b9989d92070aac/src/DynamoDb/StandardSessionConnection.php#L9)
• compound keys are now supported, via partitionKeyAttribute/sortKeyAttribute.
• Implemented deleteMany/ deleteExpired (Scan/batch). deleteExpired really shouldn't ever need to be used, as you should use Dynamo's TTL setting. DynamoDbSession->allowGc defaults to false.
• Sessions now work, and will sync their ttl settings with Sesssion::timeout/ini session settings.
• Implemented the minimum for queue, until we have a better idea of how that is going to work with Craft

Note: this branch is what is currently running on demos via dev-cloud-refactor

[jasonmccallister]

LGTM!