Property: support fractions in constant matching part of RESULT specs (experiments)

Use DefinedConstant.parseDouble based parsing to handle fractions. For
BigRational, this is already supported via BigRational.from()

+ test case

prism-tests/functionality/verify/exact/exact-experiment-1.prism

@@ -0,0 +1,12 @@
+// test case for experiments using fractional constants and fractional RESULTs in the property file
+
+dtmc
+
+const double p;
+
+module M1
+  s: [0..2] init 0;
+
+  [] s=0 -> p:(s'=1) + 1-p:(s'=2);
+  [] s>=1 -> true;
+endmodule

prism-tests/functionality/verify/exact/exact-experiment-1.prism.props

@@ -0,0 +1,6 @@
+// RESULT(p=0): 0
+// RESULT(p=1/3): 1/3
+// RESULT(p=2/3): 2/3
+// RESULT(p=1): 1
+P=?[F s=1]
+

prism-tests/functionality/verify/exact/exact-experiment-1.prism.props.args

@@ -0,0 +1,3 @@
+-hybrid -const p=0:1/3:1
+-explicit -const p=0:1/3:1
+-exact -const p=0:1/3:1

prism/src/parser/ast/Property.java

@@ -41,6 +41,7 @@ import prism.PrismException;
 import prism.PrismLangException;
 import prism.PrismNotSupportedException;
 import prism.PrismUtils;
+import prism.DefinedConstant;
 import prism.Point;
 import prism.Prism;
 import prism.TileList;
@@ -189,7 +190,7 @@ public class Property extends ASTElement
 						match = false;
 					// Check doubles numerically
 					else if (constValToMatch instanceof Double)
-						match = PrismUtils.doublesAreCloseRel(((Double) constValToMatch).doubleValue(), Double.parseDouble(constVal), 1e-10);
+						match = PrismUtils.doublesAreCloseRel(((Double) constValToMatch).doubleValue(), DefinedConstant.parseDouble(constVal), 1e-10);
 					// if constant is exact rational number, compare exactly
 					else if (constValToMatch instanceof BigRational)
 						match = BigRational.from(constVal).equals(constValToMatch);