order_columns doesn't work with foreign keys

[David Barbour]

This commit fixed rendering of columns based on a parent model's field:

https://bitbucket.org/pigletto/django-datatables-view/pull-request/3/columns-may-reference-foreign-keys/diff

But order_columns still can't pull from foreign keys. You get the following error:

"DataTables warning: table id=ProductTable - (1054, "Unknown column 'parent.parent_attr' in 'order clause'")"

[Maciej Wisniowski]

resolve issue #5

→ <<cset 1f8524862de4>>

[Maciej Wisniowski]

have a look if this commit works for you

[David Barbour]

It works great now, thank you!

[Terence Lew]

Fpreign keys also do not seem to play well with searching/filtering by DataTables. Would raise alert: "DataTables warning: table id=XXX - Related Field got invalid lookup: istartswithRelated Field got invalid lookup: istartswith"