opportunity: restrict modification of old entries

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
opportunity: improve look of welcome message

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
opportunity: nicer meetup creation confirmation

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
opportunity: always show at least 5 answer fields

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
xymus.net: update xymus.net nitcorn config to include an opportunity client

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
xymus.net: opportunity use site's header

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>