new HTTP api to manage templates

Following the latest change in manager to provide a better distinction between templates &
processes, the HTTP API has been changed as well. `processes/*` resources have
been replaced by the following REST api:

* GET `/apps` -> all apps
* GET `/apps/<appname>` -> get all templates for this application
* POST `/apps/<appname>` -> create a template
* HEAD `/apps/<appname>/<template>` -> is template existing?
* GET `/apps/<appname>/<template>` -> get the template config
* PUT `/apps/<appname>/<template>` -> update the template config
* DELETE `/apps/<appname>/<template>` -> delete the template
* GET `/apps/<appname>/<template>/stats` -> get template stats
* GET `/apps/<appname>/<template>/numprocesses` -> get the number of processes
  launched with this template
* POST `/apps/<appname>/<template>/numprocesses` -> scale
* GET `/apps/<appname>/<template>/pids` -> get all process pids launched with
  this template
* POST `/apps/<appname>/<template>/signal` -> send a signal
* GET `/apps/<appname>/<template>/state` -> get state of the template
* POST ``/apps/<appname>/<template>/state` -> start,stop or restart all
  processes in a template.