along with a new 'type-format' setting that allows
to choose the output format for the "Type" column.
The options implemented for this setting are:
'mime' : Output from g_content_type_get_mime_type().
'description' : Output from g_content_type_get_description().
'category' : It uses the corresponding generic icon
of the mime type to group by categories (aka basic types).
This produces a more compact output than previous options,
and allows for type families to be grouped together, so eg.
after sorting by "Type" column, jpeg and png images will
be placed together, or the various types of archiver files
will also be grouped together.
This format was copied from and currently used by Nautilus
list view, so we also improve consistency with Nautilus.
Bugzilla entry for Nautilus implementation is:
https://bugzilla.gnome.org/show_bug.cgi?id=683722
The list of type families or categories can be checked on:
https://developer.gnome.org/icon-naming-spec/#mimetypes
This 'category' format is set as default.
Issue #362
The old default of 148px doesn't work everywhere. Instead, pick a
default value of -1 and measure() the sidebar widget in the
filechooserwidget in that case. Other values >= 0 are still handled as
before.
