Support stained glass & clay, coloured carpets etc. with custom LogBlock config.

 * Add config/LogBlock/materials.yml to plugins/LogBlock/ on the server to
   customise material names.  This is optional.  Watson will still work with
   the default names supplied by LogBlock.
 * Names very closely align with those shown in the Minecraft client, but
   correct a couple of minor grammatical errors, e.g. "stone bricks stairs"
   are renamed to "stone brick stairs".
 * Slabs in the upper half of a block have a name like "upper dark oak wood slab",
   allowing Watson to distinguish them from the same slab type in the lower
   half of the block.
 * A more general solution to displaying exact blocks will come later with
   rendering optimisations and a generic logging plugin supporting a plugin
   channel for client communications.