Remove support for jdk 5

During testing for the upcoming 1.2.3 release, it appears that using a jdk 5 compiler with Roo-generated projects specified with the java version of 5 either do not compile correctly or have startup errors in tomcat. Since there are a few hacks in the code to add specific java 5 dependencies (and these do not appear to be getting added to the war pom), and that databases such as postgres can make use of the jdbc4 driver in java 6 and 7, it is decided that java 5 support will be dropped. The Roo shell requires java 6 anyway to execute.