Completed the maze example
- Renamed create-cheapest-path-constraint to cheapest-path-constraint
for consistency with other constraint-returning functions
- Use cheapest-path-constraint in the maze example
The returned result now contains a simpel solution structure instead of
the internal node
Also got the peg_solitaire example back to its original state, where
just the solution counts, not the number of runs with a single peg.
Documentation and very simple example problem