Allow for spaces in request URL

These changes allow spaces in arguments in the URL request (mainly for custom tags).

For example:

"http://edda/view/instances;tags.Some Tag=This Value;_expand:(tags:(Another Tagname))"

would be encoded by a browser before submission as:

"http://edda/view/instances;tags.Some%20Tag=This%20Value;_expand:(tags:(Another%20Tagname))"

These changes URLDecode the query string, and also allow the expressions in Field Selector to contain spaces.