Move functions to Utility class

[mambax7]

We should move the standard functions from /class/Utility.php to /class/Common/SysUtility.php, like what we have in Suico:
https://github.com/XoopsModules25x/suico/blob/master/class/Common/SysUtility.php

Then make the Utility class inherit from SysUtility:

class Utility extends Common\SysUtility

as here: https://github.com/XoopsModules25x/suico/blob/master/class/Utility.php

and then move all the module specific functions from /include/functions.php to the Utility class, while making them all "static"

This way we'll remove them from the Global space

[ggoffy]

can you please create a directory on github (e.g. under https://github.com/XoopsModules25x) for all these common files
then I can always implement the last version, or fork it to contribute,...