New module configuration facility, and some improvements.

- Added the ModuleConfig table, to provide modules an easy way to store their configuration parameters, with I18n, if required.
- Added the module config loop
- Added getConfigValue and setConfigValue static helper methods to BaseModule to offer an easy way to get/set a module parameters
- Refactored the Cheque module, to use the new ModuleConfig, and send an email to the customer when its payement is received.
- Added the wysywig.js hook to official hooks, so that any page which needs a WYSYWIG editor will only have to put this hook in the JS section to get one.
- Refactored Tynimce according to wysywig.js hook
- Moved cart emptying in the Order action, triggerred by the ORDER_AFTER_PAYMENT event