[WIP]: Create and edit ProjectPage resources

[eatyourgreens]

Adds a helper because project pages use a different API route from other resources.

Adds translation keys so that page titles and contents can be editted.

[eatyourgreens]

/api/projects/{project_id}/pages?url_key={url_key} doesn't return pages in all languages for that URL key. I guess the API request is filtered by language somewhere.

[simoneduca]

Looks like pages language param is hardcoded to en https://github.com/zooniverse/Panoptes/blob/master/app/controllers/concerns/pages.rb#L48

[srallen]

Yep, we discovered this while working on the lab for organizations. I opened a Panoptes issue in case you missed it: zooniverse/panoptes#2348

[simoneduca]

I saw it, but thanks for linking it here!

[eatyourgreens]

Superseded by #46