General cleanup of bashrc.

Removed some things I never use and adjusted comments. Also added swd()
to the save-directory stuff; it switches to saved directory while
setting the current one as the saved one (sort of like cd -, only it
still acts as sd and gd in future).
change keyboard layout toggle

Now changes the console layout (with loadkeys) instead of the x layout
(with xkbmap), as the former is far more useful (when don't you have the
switch when in an X session?)