Support utf8mb4 if the database does. Fixes #535

What MySQL calls "UTF8" is actually a subset of the full unicode specification.
It doesn't accept 4-byte UTF-8 characters.  Proper support is called "utf8mb4"
and is, these days, fairly common (Ubuntu 10.04LTS's bundled MySQL does not
support it, but later ones do)

Detection of utf8mb4: "SHOW CHARACTER SET WHERE charset='utf8mb4';" returns at
least one row

Conversion of pre-existing DBs: this was easy, we already had code in the
updater for this for when we started enforcing utf8. It was version-bumped and
set to update to either utf8mb4 or utf8, depending

Making it use utf8mb4 in the database connection: Actually hard.  Connector/J
5.1.13 or newer should autodetect this, but in my testing it didn't
(http://dev.mysql.com/doc/relnotes/connector-j/en/news-5-1-13.html)

As such, if utf8mb4 has been detected, I've added code that should manually
execute "SET NAMES utf8mb4;" on all new connections.

If a database does not support utf8mb4 (rare these days) I've added code to
strip these characters before DB insertion; they won't be recorded correctly,
but it'll avoid the exception from issue #535

src/main/resources/plugin.yml

@@ -1,5 +1,5 @@
 name: ${project.name}
-version: '1.91'
+version: '1.92'
 author: DiddiZ
 authors: [md_5, ammar2, frymaster]
 website: http://dev.bukkit.org/server-mods/logblock/