brother-brscan3: modified template file and deleted udev rule

The template file avoid the dependencies on brother-xxxx-lpr and
brother-xxxx-cupswrapper so anyone with a brother printer/scanner
could install it and get the scanner part of the printer work.

The udev rule create a problem with the printer part so it is moved
in brother-xxxx-cupswrapper package. A note in the Wiki page explain
the needed configuration step to make the scanner working for all
users

Regards

Carlo

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