* Added copy/move-as (copy/move and rename)

* Little refactorings

* Also handle selection file for cpmv_rename()

This patch changes the mouseinterval to 0. And handles detection of
doubleclicking events internally.

This allows much faster response times for mouse clicks as nnn no longer
has to wait for ncurses to confirm what type of click it was.

It introduces a new config setting for changing how many milliseconds it
may take for a double click to be registered.

* unmount() ask for target if not found

unmount() now properly asks for which target to unmount if it cannot
automatically deduce which folder to unmount.

* no more automatic unmounts outside of cfgdir

KDE dragon player collides with the name of the drag/drop dependency. On
archlinux the binary is renamed to `dragon-drag-and-drop`.

This change tries `dragon-drag-and-drop` before defaulting to `dragon`.

* Added 2 plugins for drag and drop support

These scripts uses https://github.com/mwh/dragon
and curl.

It allows nnn to drag and drop files either to other programs, or to
itself.

* added link to dependency and spelling

* added drag/drop-file scripts to readme table

* Implemented edit selection buffer

* Added checks and changed keybind

* Forgot check and style fixes

* Don't work late at night again

You forget things when you're tired

allow multiple make targets being specified at once

do build configuration with variables instead of targets