speed up solver by using fastutil instead of standard Java collections
improved ColorAreaGroup, speeding up solver
Merge branch 'master' into fastutil

Conflicts:
	src/colorfill/solver/DfsSolver.java
Merge branch 'master' into fastutil

Conflicts:
	proguard_config
	src/colorfill/model/Board.java
	src/colorfill/model/ColorArea.java
	src/colorfill/model/GameState.java
	src/colorfill/solver/AbstractSolver.java
	src/colorfill/solver/ColorAreaGroup.java
	src/colorfill/solver/DeepDfsStrategy.java
	src/colorfill/solver/DeeperDfsStrategy.java
	src/colorfill/solver/DfsSolver.java
	src/colorfill/solver/DfsStrategy.java
	src/colorfill/solver/GreedyDfsStrategy.java
improved solver performance
(ColorAreaGroup contains an array instead of a Map)
Merge branch 'master' into fastutil

Conflicts:
	src/colorfill/ui/Starter.java
improved performance of DfsSolver
Merge branch 'fastutil'

Conflicts:
	src/colorfill/ui/Starter.java