Add support for libtermkey, including an escape sequence to enter/exit that mode [was: Add keys preset for CSI codes. (libtermkey)]

There is a solution to legacy terminal input inconsistencies, proposed by LeoNerd, that he's described here: http://www.leonerd.org.uk/hacks/fixterms/. The idea is to use unambiguous escape sequences for all possible physical key inputs. This scheme is implemented in libtermkey. Making a preset with these mappings would greatly help software that use libtermkey (like NeoVim). For example, it solves this issue.

Most of escape sequences that need to be added are following:

Ctrl-Escape     ^[[27;5u
Ctrl-Backspace  ^[[127;5u

Shift-Tab       ^[[Z
Shift-Escape    ^[[27;2u
Shift-Backspace ^[[127;2u
Shift-Space     ^[[32;2u

Ctrl-h ^[[104;5u
Ctrl-i ^[[105;5u
Ctrl-m ^[[109;5u
Ctrl-[ ^[[91;5u

Alt-Up    ^[[1;3A
Alt-Down  ^[[1;3B
Alt-Left  ^[[1;3D
Alt-Right ^[[1;3C

I would make a PR, but I have no idea how to edit plist correctly.