keybinder: add keybinding to sync clipboard to primary selection

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
gpasted: use the new keybinding

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
Merge branch '3.0'

* 3.0:
  gpasted: use the new keybinding
  keybinder: add keybinding to sync clipboard to primary selection