Define key to more easily set a new url for the query

Remove comment that I don't know why is there because it seems to work
for me.
update version to 0.6.3
Add Robert Syme to people with copyright

(this should have been done a long time ago)
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
Add comment about using -*- mode: sparql -*-
use url-hexify-string instead of http-url-encode

It is always better to use built-ins rather than homegrown
add doc string to sparql-result-show-response