add global column to challenges and implement filtering for the column

[CollinBeczak]

Related Frontend: https://github.com/maproulette/maproulette3/pull/2382

Resolves: https://github.com/maproulette/maproulette3/issues/2373 & https://github.com/maproulette/maproulette3/issues/2350

This PR adds support for a new column in the challenges table called is_global. The challenges.is_global column represents if a challenge is classified as global, currently a challenge is classified as global if it is wider than 180 degrees (half the maps width) or taller than 90 degrees (half the maps height).

A new .sql file was added to update the global column for challenges that currently exist. This column will also be set when a challenge is created or enters a ready status.