Add src/crypto.properties to .gitignore
Reworked build.xml to improve key handling.

Previously, the build.xml would automatically create a single
private / public key pair to protect SSL communications between
the clients and the server, with the private key copied into
the server's ganymedeServer.jar and the public key/cert copied
into the client ganymede.jar and ganymedeAdmin.jar.

This autogenerated key pair and cert were also used to sign the
client jars.  With Java 1.7u40 and later, the JVM no longer accepts
self-signed certs for jars distributed with Java Web Start, which is
the common mode for deploying the Ganymede clients.

This commit separates the key pair and cert used for the SSL
communications from the private / public key pair that has necessarily
been authenticated by a certificate authority recognized by the
Java runtime environment distributed by Oracle.
Added better documentation for the crypto properties in build.xml
Changed the server/client ssl keystore names to match build.xml

These names are more self-explanatory than the old ones.
Fixed up some reference errors in ssl key generation in build.xml
More tweaks to the build.xml in keeping with RMISSLClientSocketFactory