* ExpressionUtils: Added expressionToZ3 method, which transforms certain
ITerms to z3 Exprs.
* MANIFEST.MF: Added com.microsoft.z3 to required plug-ins.
* McdcTestSuiteGenerator: Now uses formalRequirementMcdcToZ3 and
expressionToZ3.
* McdcUtils: toZ3 was renamed to formalRequirementMcdcToZ3 as this
method now only transforms FormalRequirementMcdc to a z3 Expr.
* TestingModelElementFactory: Removed checks because they are already
done by the code editor.
* TestMcdcUtils: Adjusted tests according to the changes

Issue-Ref: 3596
Issue-Url: https://af3-developer.fortiss.org/issues/3596


Signed-off-by: Ludwig Dickmanns <dickmanns@fortiss.org>