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

doc/RELEASE.txt

@@ -14,4 +14,7 @@ Made Gurobi an optional dependency
 
 Version 0.5.0
 Added the oj! Algorithm (ojAlgo) solver
-Updated dependencies
\ No newline at end of file
+Updated dependencies
+
+Version 0.6.0
+Moving augmenting the current ilp-solvers with lbjava's ilp-solver
\ No newline at end of file