Remove extra static string.

* Initial commit of sessions implementation

* Reduce code duplication

* Move load session to program flag -e

* Fix context initialization problem when loading session

* Add pinned directory to session and reduce session file size

* Make load_session print an error if exists and few minor adjustments

* Refactor session's file structure

* Initialize required structures in load_session before loading

* Add load session dynamically, restore last session, and extra fixes

* Fix indentation

* Add sessions documentation to man page

* Update fish completions with sessions and make some improvements

* Move to single keybinding session management and add help info

* ESC when asked to insert session name behaves better

* Add sessions completion for bash

* Remove pinned dir from session and minor code refactors

This reverts commit e226e8c889.

This is a conveninece for nav-as-you-type mode.
With this program option, on pressing ^P, the filter is  executed as cmd.

-d is to show detail mode
-H is to show hidden files
-l is retired

The new location is ~/.config/nnn/.lastd

This may affect issue #227 but the defunct processes do not use any memory and exit when nnn exits. I guess that happens because of xdg-open using an intermediate script.

However, if we do not detach xdg-open, the child process is killed when the terminal is closed which is a severe problem.