Otherwise, several --info switches will not properly override each other

This fixes "feh -D -1 -D 1" and similar starting the slideshow in paused mode
even though the last -D option specifies autostart.

closes #458

This changes the behaviour of "feh --start-at FILENAME" as follows:

Previously, this would cause feh to load all files in the current
working directory, since no files or filelists were specified on the command
line.

Now this is a special case: feh will extract the directory component from
FILENAME, load all files in that directory, and display FILENAME.
This way, it's possible to use "feh --start-at ~%f" in XDG Desktop files
and browse files in feh using the prev/next keys

Closes #372
Closes #420

Closes: #124

Passing an empty string to the --geometry option will enable fixed geometry mode without having to specify anything else

See #278

Uses the camera-generated thumbnail to display RAW images that could otherwise not be loaded.

This introduces a new feh_should_ignore_image function which is called
at appropriate places in those modes to skip images which are loadable but
undesired.

Closes #381

This option allows you to change the default imlib2 image cache size of 4 MiB.

might resolve #333 and #348

Sort filelist by dirname, then by name. This results in file entries
sorting before subdirectory entries.

Useful in conjunction with upcoming prev_dir and next_dir navigation
actions.

Purpose of "--no-recursive" option is disabling effect of "--recursive" option that enabled by user's theme.