Query Parameters Now Require Escaped Format for NULL Support

Now it's expected that query parameters are represented in "escaped" format. For example, to pass string a<tab>b you have to write a\tb or a<tab>b and respectively, a%5Ctb or a%5C%09b in URL. This is needed to add the possibility to pass NULL as \N. This fixes #7488. #8517 (alexey-milovidov)