Tagger: allow people to enter a count before pressing a species key when adding a new species to an image

Allow users to enter a numeric count, capped at 20, before they press a species key. This only applies to new species being added to an image.

Currently, to add 15 of one species, the user needs to add one of the species and then either press the species key 14 more times or adjust the count displayed next to the specie. Since most counts of species are done before adding the specie, its less work to also type in the number of animals found and then their key. For example, pressing keys `1 + 5 + R` could create a new entry of Rabbits and set the count to 15.

This does not apply to Ghosts which can only have the count of 1

This only applies when tagging single images. If multiple images are selected the numeric count isn't available.