firstletter => search patrons with surname begins with this pattern (currently only used for 1 letter)
categorycode and branchcode => search patrons belong to a given categorycode or a branchcode
searchtype: can be 'contain' or 'start_with'
- searchfieldstype: Can be 'standard', 'email', 'borrowernumber', 'phone' or 'address'
+ searchfieldstype: Can be 'standard', 'email', 'borrowernumber', 'userid', 'phone' or 'address'
=cut