Added exceptions for undefined policies and made them be thrown in
SDPlannerPolicy objects if the policy is undefined.

Fixes #5
burlap.behavior.singleagent.learning package fully documented.
removed unnecessary imports
removed unncessary imports
added some helper methods for working with multi-target relational
attributes
added NullHeuristic, a GoalCondition TerminalFunction wrapper, and
another helper method to episode analysis that allows the client to
specify the delimiter in an returned action plan string.
Added value unset exception that is thrown if a discrete value or real
value for a an OO-MDP object is not set and is queried.

Fixes #6
Fully documented burlap.datastructures and burlap.debugtools
added additional helper method to GraphDefinedDomain domain generator
class. The added method spits back the int identifier of the graph node
for a given input state.
the grid world domain, graph defined domain, and blocksworld domain
related classes are documented.
ValueIteration DPrint calls now use its reported debug code.
added functionality for deterministic planners to use terminal functions
in additional to the goal conditions that specify terminal states that
are not goal states.
lunar lander domain fully documented.
some grid game documentation
Fixed bug in grid games. added full transition dynamics generator for
grid games (rather than just the sampling method). burlap.domain fully
documented.
documentation for stochastic games behavior
fully documented burlap.behavior.stochasticgame
burlap.behavior.vfa fully documented.
Renamed an option to something more descriptive; added policy defined
methods to policies. Also, BURLAP is now fully documented.
Fixed bug in value function planners that would occur if a non-zero
value function initialization was used.

Also added method to the ValueFunction planner class for changing the
value function initialization method so that any value function planner
can make use of it.