xterm: use full resource namespaces
vim: change key mappings for increasing/decreasing the font size

 * use alt++ or alt+= to increase the font size
 * use alt+- to decrease the font size
 * use alt+0 to reset the font size
xterm: change key bindings for increasing/decreasing the font size

 * use alt++ or alt+= to increase the font size
 * use alt+- to decrease the font size
 * use alt+0 to reset the font size
urxvt: add key bindings
xterm: change paste key binding to be the same as in urxvt

 * use alt+mouse_middle_button to paste from clipboard
urxvt: update extension submodule
urxvt: use fullscreen plugin; add key binding
urxvt: change paste key binding to be the same as in xterm

 * use ctrl+shift+c for copy
 * use ctrl+shift+v for paste
 * use alt+v for paste_escaped