Implement split and stitch for large data channel messages in Android

[cereallarceny]

This was already done in syft.js: https://github.com/OpenMined/syft.js/issues/78

This will also need to be done for Android. You should read these two classes so that you fully understand the problem and theoretical solution:

• https://github.com/OpenMined/syft.js/blob/master/src/data_channel_message.js
• https://github.com/OpenMined/syft.js/blob/master/src/data_channel_message_queue.js

[vkkhare]

Part of #33