add the abity to use a config setting in the setup.xml 'requires' opt…

…ion, this allows dynamic system menus.

example:
<item level="0" text="Sync NTP every (minutes)" requires="config.misc.SyncTimeUsing">config.misc.useNTPminutes</item>

if 'config.misc.SyncTimeUsing' is True or not equal to '0' it will return true and be shown, if it returns False or '0' the itm will be hidden.