Automatic table creation

[kshpytsya]

• Python DynamoDB Lock version: 0.9.1

It would be great if the library would (optionally) automatically create the locks table if it does not yet exist, or at least document how it would be possible to accomplish it on the client side.

Currently, calling create_dynamodb_table multiple times fails with

botocore.errorfactory.ResourceInUseException: An error occurred (ResourceInUseException) when calling the CreateTable operation: Table already exists: DynamoDBLockTable

error, and not calling it at all fails with

python_dynamodb_lock.python_dynamodb_lock.DynamoDBLockError: DynamoDBLockError: UNKNOWN - An error occurred (ResourceNotFoundException) when calling the GetItem operation: Requested resource not found

At least make a distinct error code for the case of missing table instead of the unhelpful DynamoDBLockError.UNKNOWN.