OAuth 1: Fix special characters in query strings

[Alanaktion]

This changes the OAuth 1 HMAC signature generation to support query strings in the path that include special characters, and fixes query strings that use a PHP-style array syntax for the key.

For example, foo[bar]=1 would previously trigger an error, but is now handled correctly, encoding the key to foo%5Bbar%5D before hashing.

Encoding of query values is changed to use RFC 1738-style plus encoding, then full RFC 3986 encoding, which seems to match most implementations. This at least fixes values with spaces when authenticating against the Magento 2 REST API, and matches how Postman encodes the value in its HMAC process.