remove path from config. Fix update.php for improper constant definition

check.
add a timeout on curl request for update check

because if you don't have that, it will continue indefinitely and
apache needs a restart… It happens when you need a proxy setting, but
it's not here.
add default config into elabftw.sql file

This way, everything is imported in one step, from the file, as now
there is no more this $path to insert in the sql config, so it's all
good. This is done to facilitate docker install also.
remove stuff from sql leading to errors