Minor Javadoc updates to aid readability.
Adding new crawler module for crawling the graph in the background.
Adding simple test harness ready to test the new module (WIP).
Adding graph crawler and basic implementation (WIP).
Adding code to plug a node inclusion strategy into the crawler and to actually do some work given the crawling context.
Updating test in light of this change.
Improving JavaDoc so that module authors know what methods can be safely overridden without needing to look at the code.
Replacing deprecated code with new alternative.