Convert calibre modules to ebook_converter.

Here is the first batch of modules, which are needed for converting
several formats to LRF. Some of the logic has been change, more cleanups
will follow.

ebook_converter/ebooks/oeb/transforms/page_margin.py

@@ -9,8 +9,8 @@ __docformat__ = 'restructuredtext en'
 import numbers
 from collections import Counter
 
-from calibre.ebooks.oeb.base import barename, XPath
-from polyglot.builtins import iteritems
+from ebook_converter.ebooks.oeb.base import barename, XPath
+from ebook_converter.polyglot.builtins import iteritems
 
 
 class RemoveAdobeMargins(object):