Make "@" optional for implicit parameters

Make the "@" prefix for implicit parameters optional.     GET http://host/service/EmployeesByManager?ManagerID=3 If the parameter matches a system query option, the system query option is used. To be unambiguous and future proof, use the "@" prefix. Keep the "@" prefix in the path for explicitly introduced parameter aliases in order to disambiguate within the path, and in the query option to match the alias within the path.

https://www.oasis-open.org/committees/download.php/61629/odata-v4.01-wd03-part2-url-conventions-2017-09-22.docx https://tools.oasis-open.org/version-control/browse/wsvn/odata/trunk/4.01%20spec/ABNF/odata-abnf-construction-rules.txt?op=diff&rev=1071 https://tools.oasis-open.org/version-control/browse/wsvn/odata/trunk/4.01%20spec/ABNF/odata-abnf-testcases.xml?op=diff&rev=1071