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/polyglot/binary.py

@@ -7,7 +7,7 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 from base64 import standard_b64decode, standard_b64encode
 from binascii import hexlify, unhexlify
 
-from polyglot.builtins import unicode_type
+from ebook_converter.polyglot.builtins import unicode_type
 
 
 def as_base64_bytes(x, enc='utf-8'):

ebook_converter/polyglot/functools.py

@@ -4,7 +4,7 @@
 
 from __future__ import absolute_import, division, print_function, unicode_literals
 
-from polyglot.builtins import is_py3
+from ebook_converter.polyglot.builtins import is_py3
 if is_py3:
     from functools import lru_cache
 else:

ebook_converter/polyglot/html_entities.py

@@ -2,7 +2,7 @@
 # vim:fileencoding=utf-8
 # License: GPL v3 Copyright: 2019, Eli Schwartz <eschwartz@archlinux.org>
 
-from polyglot.builtins import is_py3
+from ebook_converter.polyglot.builtins import is_py3
 
 if is_py3:
     from html.entities import name2codepoint

ebook_converter/polyglot/urllib.py

@@ -4,7 +4,7 @@
 
 from __future__ import absolute_import
 
-from polyglot.builtins import is_py3
+from ebook_converter.polyglot.builtins import is_py3
 
 if is_py3:
     from urllib.request import (build_opener, getproxies, install_opener,  # noqa