Ported "String.ToNumber" and updated relevant test cases

- Ported and migrated "String.ToNumber"
- Updated relevant test cases
- Changed "Formula" nodes into equivalent nodes in the .dyn files

Test cases which are now passing:
- Dynamo.Tests.ListTests.Combine_ComplexTest
- Dynamo.Tests.ListTests.DropEveryNth_ComplexTest
- Dynamo.Tests.ListTests.ShiftListIndices_Complex
- Dynamo.Tests.ListTests.SplitList_ComplexAnotherExample