update what information we capture related to sightings

[micheal-w-wells]

Currently the app treats sightings and moose at a very granular level, we are going to 'roll things up':

• [x] Instead of 'add a sighting' we'll change it to 'record your sightings'
• [x] instead of details for each moose, just prompt for 'how many moose did you see?'
• [x] instead of male/female/age, just prompt for over what days did you see them (start and end date)

tick related info will be in another ticket.