Add an indicator for characters left before hitting the limit

Changes introduced:

1. A request to /api/statusnet/config.json is being made so that we fetch the text limit, site name and whether the registrations are open from the backend.
2. The aforementioned info was removed from /static/config.json
3. A number indicating the amount of characters left before hitting the text limit is being displayed.

I have returned.

marked as a Work In Progress

unmarked as a Work In Progress

changed the description

merged

mentioned in commit b0f248c4