Commerce: Availability

This module provide a booking system to Commerce module.

I started this project as the Rooms module doesn't provide enough option to customize it for any event system.

I used some of the Rooms module and Stock module features. Most of its code comes from these both modules.

From Rooms module I took the availability management system. From stock module I took the rules to block the transaction.

Features:
- Add a booking date field to line items
- Add several rules to block transactions if the product is not available on the booking date
- Add a availability management system, based on the Rooms module one to increase or decrease availability on selected periods.

This module could be a good direction for the generalization of the Rooms module, and its complete integration to the Commerce module.