Add image configuration for tomcat appliance

After this change you can build tomcat image like this:

   make image=tomcat

and then run it like this:

   scripts/run.py

Because osv-apps repo is not yet linked as submodule, you need to edit
config.json and specify location for "tomcat" module, like this:

{
   "modules": {
   	"mgmt": {
		...
	},
        "tomcat": {
                "type": "direct-dir",
                "path": "${HOME}/src/osv-apps/tomcat"
        }
   }
}

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Add image configuration for cassandra

This allows to build a runnable image like this:

   make image=cassandra

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>