Implemented the ability to disable server-side texture pack prompts at login.  Does not conflict with SpoutcraftAPI's ability to force the texturepack from the server if the Admin so desires.  This only disables the built-in Prompt ability from Minecraft Server itself.

By Request: https://spoutdev.atlassian.net/browse/SPOUTCRAFT-530, Enjoy!

Signed-off-by: Mike Howe <mike@mcsnetworks.com>