Create transport buffer max size limitation

[elliotmr]

right now it would be easy to cause the host program to crash by creating a message that has a Very Large Number as it's size. There should be a setable max size which causes the response to be thrown out.

Note: In general such a system will cause a de-synchronization in the request/response nature of the plugin communication. It is probably best to terminate the plugin if this limit is reached.