Added IDA* implementation, visualisation and unit test. 

Added IDA* implementation, visualisation and unit test.

* IDA* supports all optional properties that the A* pathfinder has. 
* It adds a max execution time to overcome "too much recursion".
* The "Node.jumptest" property was made generic so IDA* can use it for visualisation as well.

A demo has been published here: http://gerjo.github.io/PathFinding.js/visual/