Bug 4281: Reports dictionary supports only 1 field selection

Bug 4281: Reports dictionary supports only 1 field selection

The reports dictionary allows the user to select several fields, but
only 1 is used.
The interface is quite confusing.
This patch removes the multiple selection and permit to select only 1
field.

Test plan:
1/ Create a report dictionary (reports/dictionary.pl)
2/ On the step 3, confirm that only 1 field can be selected

Confirm there is no regression on this tool.

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
(cherry picked from commit e6d9882a14068d257dd48e4cbfb3381fe2274a8c)
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>