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 payment 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 module according to wysywig.js hook
- Moved cart and order flush in the Order action, triggered by the ORDER_AFTER_PAYMENT event
- A few minor improvements

This annotation is only used by your IDE and never by php so importing the namespace Thelia\Model\Hook is not needed.