src/main/webapp/WEB-INF/web.xml: Show Poubatal by default and remove GuestBook configuration
src/main/java/fr/univnantes/atal/poubatal/DataManager.java: Configure the proxy from the environment

* src/main/java/fr/univnantes/atal/poubatal/DataManager.java
(DataManager): Retrieve proxy settings from http_proxy.