Fix url support for receive_date_high & receive_date_low

Fix url support for receive_date_high & receive_date_low

This ensures that the following url params are supported
receive_date_high=20180101
receive_date_low....
contribution_cancel_date_high
contribution_cancel_date_low
invoice_number=

Note that in doing this I fixed the new & somewhat experimental default function to use field uniquenames
rather than field names (as this is how they are added to the form & it was required for cancel_date.

Support for receive_date_relative=this.day etc would be trivial but not yet tackled

Also I see that we historically support 'start' and 'end' I think we can tackle this by doing something like
if start is set then ->set('contribution_date_low' - probably with a deprecation notice)
I will leave for a follow up though