fix checking satisfactory continuous model of MinSpareNode and MaxSpareNode constraints.
Merge branch 'develop'

Conflicts:
	SpareResource/src/main/java/btrplace/model/constraint/MaxSpareNode.java
	SpareResource/src/main/java/btrplace/model/constraint/MinSpareNode.java
	SpareResource/src/test/java/btrplace/solver/choco/constraint/CMaxSpareNodeTest.java