Changed cow and plot retrieval methods interfaces

Now the login is optional, and it won't filter by it when
not passing it.
Removed url from views dictionaries

Now we get the url from the request directly in the
chameleon template.
Updated the orders management screen

Now the admin user can see a table (though awful looking) with all
the orders data, and their status can be changed via a combobox.
And users can see the same table with their own orders, with the
form for submitting new ones above it.