Add simple mechanism to select plural word form

The utility gets passed a number and both singular and plural form
of a word. It returns the singular form for number == 1 and the plural
form for all other cases (including number == 0).
Use correct plural verb on upload success page

"1 photo _was_ uploaded"
vs
"2 photos _were_ uploaded"
Merge pull request #1060 from pixelistik/978-plural-was-were

Correct plural "was/were" based on count