Children improvements

This pull request contains :
 - Children informations retrieving from webservice
 - Description generation wizard
 - Moving projects into child_compassion project
The module child_compassion should be installable alone as it doesn't depend on module sponsorship_compassion. It is weird to define menus for the compassion_child module in the sponsorship_compassion module. 
Even though they are related, we should respect the inheritance model and have menus for child module inside it, and maybe an override in the sponsorship module.