Move og.module into main project directory

Drupal 7's Update Manager is unable to handle modules that have the primary module stored in a subdirectory rather than in the main directory, specifically "og/og/og.module" instead of "og/og.module". As a result, for D7 the og.module needs to be moved to the main directory, which will also help avoid a lot of support requests down the road.

Further discussion continues in #986616: Update Manager fails when the primary module/theme for a project lives in a subdirectory.