Added "whitelist" for rooms that can be booked, side effects: added new control mod_r...

Added "whitelist" for rooms that can be booked, side effects: added new control mod_roomReservationRoomWhitelististBox for config page, added mod_roomReservationBookingsTable::asErrors for error messages, mod_roomReservationBookingsTable::setRoom() checks if the room is whitelisted; added functions whitelistRoom(), unWhitelistRoom(), isRoomWhitelisted(), getWhitelistedRooms() in mod_roomReservationConfig; changed column layout in mod_roomReservationConfigPage::doShow() for better space utilization; added SQL table mod_roomreservation_roomswhitelist that contains the whitelisted rooms. Furthermore added member variables for controls in mod_roomReservationConfigPage as the controls mustn't be initialized in mod_roomReservationConfigPage::doShow() unless you want lost error messages.