Overriding kurento.properties location through env variables

Change-Id: Ic9a6c40627591cc2c2687abf30146a8119831923
Improved kurento.properties loading (1. jboss.server.config.dir ; 2. kurento.properties.dir ; 3. Servlet Context)

Change-Id: Ie7d9143ca5be99eb256e07076f4a74fc521a6e57