Revert "Remap prefix to Ctrl-Space"

This reverts commit 58a0c0c0cbd051c5938eb6a843b0d06d102b9081.
Minor tmux tweaks.

- Start windows at 1 rather than 0 (easier to navigate to on the
keyboard).
- Set escape time to zero to hopefully speed things up.  Unknown side
effects.
Add dash functions
Do not warn of clobber, this is very annoying.