Allow to configure the timeoutlen.

Timeoutlen is  the time in milliseconds that is waited for a key code or
mapped key sequence to complete.
Fixed wrong display for ambiguous maps.

If there exist maps for 'a', 'aa' and 'aaa' the 'aaa' was displayed to the
user after the first typed 'a'.
Don't built completion if there is only one item.

Instead we print the item direct to the inputbox instead.