Run evince instances in different processes instead of single instance

Run evince instances in different processes instead of single instance

 - When built with DBus support a daemon is used to keep track of opened
   documents and reload them when reopened.

 - Crash recovery code has been removed.

 - Metadata migration code has been moved from main.c to ev-daemon.c, so
   that it's only run once on daemon startup.

Fixes bgo#583680, bgo#434966, bgo#497388, bgo#524633 and bgo#586087.