NOTE:
  This "ext" folder is for external jar when load. especially for JDBC jars.
  If have some exception for ClassNotFoundException or "Miss JDBC driver jar...", 
  need place the JDBC jars here and restart the web container(Tomcat/JBoss).

Addition:
  for example, deployed the "amc.war", the "ext" folder is:
  - For JBoss 6.x: 
    ../standalone/tmp/work/jboss.web/default-host/amc/eclipse/plugins/org.talend.amc.libraries_6.1.1.20151214_1327/lib/ext
  
  - For Tomcat:
    ../webapps/amc/WEB-INF/plugins/org.talend.amc.libraries_6.1.1.20151214_1327/lib/ext