Added password urlencode

This commit adds the encoding of passwords according to url standard. (See https://stackoverflow.com/a/34407620)

As the username and password get passed along to Shibboleth, they have to be encoded which caused my password to not be accepted anymore. As some characters are, and some aren't, encoded this problem only occurs with users that have a very special character in their password, e.g. % or \0

This is fixed with this merge.