remove code duplication, add history, add ask for new url config

Move all base-url setting into the same function

Add a history to the prompt

Add configuration for asking for the base-url every call to
sparql-get-base-url
add easier way to set current format

it is now possible to set the format interactively and there is a
history. The history contains the commonly used formatting types by
default.
Define key for setting the format
update version number