* Replacing 'rand()' leftwover with 'rnd()' of mt19937ar
* Cleaned up script commands related with item group: 'groupranditem', 'getrandgroupitem', 'getgroupitem'
* Corrected item scripts that are using 'getrandgroupitem'
* Updated script command and item group doc
Signed-off-by: Cydh Ramdh <cydh@pservero.com>