[MERGE] New digest scheme helper protocol

The current digest scheme helper protocol have great issues in how to
handle quote <"> charactes. An easy way to solve this is to switch
protocol to a protocol similar to what we already use for basic helpers
using url escaped strings

  urlescape(user) <SPACE> urlescape(realm) <NEWLINE>

Note: The reason why realm is urlescaped is to allow for future
expansions of the protocol.

The default is still the old quoted form as helpers have not yet been
converted over. But once the helpers have been converted default should
change to urlescaped form.