Add method to run the compressor starting from a particular compressor-state

[Azrenbeth]

BUILDS ON azren/config_integration_tests

Added the method continue_run() to lib.rs:

• allows you to give a specific compressor state to start from
• runs the compressor on a chunk of the room state
• returns the compressor state and what state it got up to in the room

This can be used to run the compressor in small chunks on rooms and still get the same state_group structure as if the room had been compressed all in one go.