Code style cleanups

Add keyword arguments. Sort arguments and models.
Move literals to their own module. Prepend handler_ to
signal handlers.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/document_indexing/html_widgets.py

@@ -14,7 +14,7 @@ def get_instance_link(index_instance_node):
     Return an HTML anchor to an index node instance
     """
     return mark_safe(
-        '<a href="{url}">{text}</a>'.format(
+        s='<a href="{url}">{text}</a>'.format(
             url=index_instance_node.get_absolute_url(),
             text=escape(index_instance_node.get_full_path())
         )
@@ -35,7 +35,7 @@ def index_instance_item_link(index_instance_item):
         icon = ''
 
     return mark_safe(
-        '%(icon)s&nbsp;<a href="%(url)s">%(text)s</a>' % {
+        s='%(icon)s&nbsp;<a href="%(url)s">%(text)s</a>' % {
             'url': index_instance_item.get_absolute_url(),
             'icon': icon,
             'text': index_instance_item
@@ -48,7 +48,7 @@ def node_level(node):
     Render an indented tree like output for a specific node
     """
     return mark_safe(
-        ''.join(
+        s=''.join(
             [
                 '&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;' * node.get_level(),
                 '' if node.is_root_node() else icon_index_level_up.render(),