[fix] replace obsolete string.join function

    categories, engines, engine_shortcuts

)

import re

import string

import sys

if sys.version_info[0] == 3:

    def getFullQuery(self):

        # get full querry including whitespaces

        return string.join(self.query_parts, '')

        return u''.join(self.query_parts)

class SearchQuery(object):