Add updated algorithm pseudocode

[bmmalone]

As pointed out by Ni, the pseudocode in our JAIR paper has several typos and other problems. The docs for the project can include a brief algorithm description and pseudocode for the main solvers (astar and bfbnb, as well as the static pattern databases).

• astar
• bfbnb
• static pattern databases
• sparse parent lists
• sparse parent tree