Replace globals by constants

[HugoFara]

LWT likes to use globals, by they are difficult to identify and edit. They should be replaced by something better adapted and more robust.

• Constants: everything in connect.inc.php and inc/settings.php.
• Session variables to put under $_SESSION: the ominous $tbpref and his friend $fixed_tbpref. $DBCONNECTION as well. $langDefs needs more work.

[HugoFara]

The same goes for functions returning always the same value: get_version and get_statuses in inc/kernel_utility.php. Version can also be constant in api.php.

[HugoFara]

For anything as connect*.inc.php, I am thinking of removing the file altogether. The new system may look like:

[settings]
server=localhost
userid=root

This is INI format, but YAML could be great as well, if anyone has another suggestion let me know!