Add the ability to 'replace footage' with an After Effects composition

When you click 'Replace footage…' in the Project panel in Premiere, if you choose an After Effects file, rather than giving you the option to select a composition from within that file, an error message reads 'The importer reported a generic error', and then the footage is replaced with a media offline error.

It should instead be possible to select a composition. This is useful when using the raw footage as a placeholder during assembly before adding effects in After Effects at a later point.