Container helpers

• sgs_IsArray - return if variable is of array type
• sgs_IsDict - return if variable is of dict type
• sgs_IsMap - return if variable is of map type
• sgs_ArraySize - return array size or -1 if variable is not an array
• sgs_ArrayPush - push the last count variables on stack to the end of the array var, then pop them from the stack
• sgs_ArrayPop - pop the last count variables off the end of the array var, optionally return them
• sgs_ArrayErase - remove the specified variable range [`at`,`at`+`count`) from array var
• sgs_ArrayFind - return the first position of item what in array var or -1 if item was not found
• sgs_ArrayRemove - remove first/all occurrence(s) of what in array var
• sgs_Unset - unset the specified index of the given dict/map variable, return if successful