Splitted admin and other views in dedicated webpack chunks (~25% reduction of chunk size for regular users)

Fix #781: Added a `check_inplace_files` management command to remove purge the database from references to in-place imported files that don't exist on disk anymore

Fix #735: library view doesn't like long titles names

Closes #735

See merge request funkwhale/funkwhale!640

Fix #737: delivering of local activities causing unintended side effects, such as rollbacking changes

This reverts commit 8b47af8b, reversing
changes made to c0055b3b.