Enable property option to use AT_TIMESTAMP shard iterator in MultiLangDaemon clients

[marcinc]

Since support for Time based shard iterators was added in #94, it would be good to enable option to pass initial timestamp for AT_TIMESTAMP iterator from properties file. This would enable Multilang Daemon clients to take advantage of this iterator type. This was previously requested in #145.

It looks like it could be achieved by simply adding appropriate Date parameter type decoder in KinesisClientLibConfigurator which would then allow use of the following property:

# app.properties

timestampAtInitialPositionInStream = 1527254694

Internally this would result in correct setting of initialPositionInStream to AT_TIMESTAMP and its initial timestamp to 1527254694.

[pfifer]

This should be fixed in 1.9.2 and should be available in Maven over the next 24 hours.

Feel free to reopen if you run into the issue again.