Add some Bindings from lem/acme, remove unused

Add some Bindings from lem/acme, remove unused

Removing rotate-windows and toggle-window-split, rarely used.

Grabbed some bindings from lem
<github.com/lem-project/lem/blob/master/src/default-keymap.lisp>.  C-h as
backspace, C-x ? as describe-key, C-x / as describe-symbol.

Some bindings inspired by acme:  Home goes to top of buffer, End goes to bottom
of buffer, up/down act as page up/down.