Add a single shell script to handle cache server startup

Rather than having separate startup scripts for memcached and hotrod, a single script should be used, which would take in a "protocol" parameter to determine which server module to start.

From my email to infinispan-dev:

"I notice you have a memcached.sh script to start the memcached server. I believe this should be something like startServer.sh, given that we are not actually starting memcached?

And perhaps the script could be reused for HotRod as well ... passing in a flag to specify which protocol to speak, perhaps something like:

$ startServer.sh -p memcached

or

$ startServer.sh -p hotrod

Perhaps org.infinispan.server.memcached.Main could be in the server/core module instead, and based on the protocol flag passed in, kick start the appropriate server? WDYT?"