Fix index increment in Signature validation

[Advaitva]

Due to the fixed index (index = 0), always the first capturing group is selected. This was creating a problem when the signature had different types parameters.

[aeberhart]

Dear @Advaitva, thanks for the fix. Could you please provide a unit test that shows the problem?

[Advaitva]

Hi @aeberhart, please have a look at the unit test in my commit. Here are the screenshots proving the same -

Original issue -

With index increment fix -

[aeberhart]

checked against the original implementation:

                    params.forEach(function (param, index) {

we translate to

            int index = 0;
            for (Object _param : _params) {

but forgot to inc the counter. The fix changed the behaviour of com.dashjoin.jsonata.SignatureTest.testParametersAreConvertedToArrays()
in that null values are treated

the failing unit test was fixed in a subsequent commit.

Thanks @Advaitva !