When people use unicode course org name(e.g Chinese) ,urllib.quote cannot format unicode char like:
```shell
>>> import urllib
>>> loc = 'i4x://创联/7302478/chapter/4ab413b41ad9447db41668bed03f149f'
>>> urllib.quote(loc)
'i4x%3A//%E5%88%9B%E8%81%94/7302478/chapter/4ab413b41ad9447db41668bed03f149f'
>>> urllib.quote(unicode(loc))
Traceback (most recent call last):
File "<console>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe5 in position 6: ordinal not in range(128)
>>>
```
so I open this pull
This commit adds all of cms.
These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).
For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.
Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>
[LMS-2370]
This is the changes for STUD-1244, which introduces the ability for Studio to display
arbitrarily nested xblocks. In this change, a new container page is introduced which can
display nested xblocks. In particular, the xblock type of 'vertical' is special cased
to be shown inline as a collapsible section. The unit page is mostly unchanged, except
that container xblock's are shown as a link to their container page, rather than being
shown inline.
