Unsatisfiable after creating a set of lazy literals

[AllenZzw]

This instance gfd-schedule.fzn.json should be satisfiable, but the solver stops with "unsatisfiable" after creating a set of lazy literals and their associated clauses without entering the constraint propagation phase.

From the logs.txt file, it seems like it is related to how direct encoding literals and order encoding literals channel with each other.

[AllenZzw]

Fixed in #78