[core] Add "merged" pango support

With this commit, it is possible to add pango directives inside every
piece that supports direct output (e.g. defaults/prefix or <module
name>/prefix) and those will be merged - i.e. it is possible to specify
defaults inside "defaults" and override/specify in the particular
modules.

core/output.py

@@ -52,7 +52,6 @@ class block(object):
         text = attr.get('full_text', '')
         if 'full_text' in attr:
             del attr['full_text']
-
         result = '<span '
         for key, value in attr.items():
             result = '{} {}="{}"'.format(result, key, value)