Remove unused customer/profile.py

profile.py is not imported anywhere, and it's get_profile_class
is a duplicate of core/loading.py:get_profile_class.
Remove call of missing checkout init function
Add the git protocol to the django-haystack dependency link

Without it, it is a malformed VCS url
Add migration help to customise models docs
Docs: Remove duplicate OSCAR_IMAGE_FOLDER entry
Add note to docs for customising classes of products.
Improve sandbox installation process

* Remove profiling middleware from default setup
* Document dependency on libjpeg
Adjust post-user-create receiver to check database state

Need to avoid situation where this signal gets raised by syncdb and the
database isn't in the correct state.

Fixes #475
Document dependency on compressor in default templates

See https://groups.google.com/forum/#!topic/django-oscar/-F1rEUX-RZA
Update installation doc

* Use `code-block` to see if that renders differently