window: Fix issues with opening files
Baobab doesn't expect that file handler doesn't have to exists for certain mime type and consequently fails when opening file with "g_app_info_launch: assertion 'G_IS_APP_INFO (appinfo)' failed" critical in such case.
It also requires only handlers which supports URIs. Consequently, for example, it is not possible to open folders in Thunar as it uses "%F" on its Exec line. But all supported URIs should be accessible over gvfsd-fuse mountpoint.
Let's replace the whole logic to open files by simple g_app_info_launch_default_for_uri() to fix those issues.
Fixes: #31 (closed)