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/utils/xml_parse.py

@@ -63,5 +63,5 @@ def find_tests():
 
 
 if __name__ == '__main__':
-    from calibre.utils.run_tests import run_tests
+    from ebook_converter.utils.run_tests import run_tests
     run_tests(find_tests)