Get rid of applet code

[lpassey]

I very much regret the loss of support for applets, but what is, is. Thus, can we remove the Applet support files out of the build? Perhaps move SOCAccountClient.java and SOCApplet.java into another folder, perhaps called "Attic" which is outside of the source tree. I wouldn't want to lose the history, but it makes no sense to include that code in the compiled jars.

[jdmonin]

Thanks for the reminder about this one.

Just as the player client runs as a Swing app, so can SOCAccountClient, so no need to remove that one. The Database.md doc describes how to launch it.

I'll clean out SOCApplet

[jdmonin]

Updated SOCAccountClient to not reference Applet class or methods: 0f59f77