Rest/Mustache issues with parsing of multipart form data

The RestPlugin has some issues with numeric and boolean data submitted via form-multipart because the data is sent quoted but expected to be unquoted.  The problems are demonstrated in the commented out testcases introduced in #296

https://github.com/fair-acc/opencmw-cpp/blob/main/src/majordomo/test/majordomoworker_rest_tests.cpp#L84-L88