Revert "jessie: Install xbindkeys directly from mirror."

This reverts commit 19c75c0959aeaf6c3a0be6c1ea2f7b3584335c0b.

xbindkeys has been added back in jessie repository:
https://packages.debian.org/search?keywords=xbindkeys
Merge pull request #656 from drinkcat/xbindkeys-jessie-revert

Revert "jessie: Install xbindkeys directly from mirror."
start*/enter-chroot: Make sure options with missing arguments are detected.

Mark the end of user specified parameters with "".

Makes sure commands like `sudo startcli -u` fail instead of outputing
confusing messages like `user exec not found`).