Add the git protocol to the django-haystack dependency link

Without it, it is a malformed VCS url
Remove call of missing checkout init function
Merge pull request #489 from tangentlabs/issue/488/django-haystack-dependency

Add the git protocol to the django-haystack dependency link
Add migration help to customise models docs
Docs: Remove duplicate OSCAR_IMAGE_FOLDER entry
Docs: Fix typo and remove duplicate word.
Merge pull request #493 from maikhoepfel/mh/fixdocs

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
Docs: Work on "customising an app".

The docs contained reference on how to keep template tags working after
overriding an app, but this information is now obsolete as they've been
moved to oscar/templatetags. Thus, this info is removed.
It is replaced by similar instructions on how to keep the Django admin
around.
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