merging with lbjava's ilp-solver interface

Changes:

• merges the two ILPSolver interfaces (in this package and the one in LBJava)
• merging the two gurobi solvers: for most of the syntax I have used that of LBJava's.

If this get's merged, we can remove IlpSolver.java, GurobiHook.java and oJAlgoHook.java from lbjava and add this illinios-inference as LBJava's dependency.

FYI @mssammon