Replace xp_mysql with MySQL Connector/NET for SQL connectivity.

* Route all NWScript and ALFA.Database SQL through the MySQL .NET
  library to avoid bugs in xp_mysql on server disconnect and
  reconnect.  _LoadAssemblies establishes the initial setup for
  the database connection, which is handled through ACR_ServerMisc
  and its existing interface for exporting arbitrary MySQL
  connections to script code.  The connection id of 0 is reserved
  the the default database connection for this purpose.

* The "canonical", standard default database connection is not
  pooled to avoid a performance (latency) penalty on each query due
  to internal transactions with the database server made by the
  client library itself.

* All modules MUST recompile with this update.

* Also, fix scripts that did not reference ALFA.Database from
  ALFA.Shared but still duplicated the code locally.  This is no
  longer supported for ALFA.Database.

* SQL logging is now to a dedicated StandardQueryLog.txt file for
  the "canonical" standard default database connection.  This log
  file is written to the NWNX4 directory and overwrites on startup.

  The log file is timestamped, unlike the xp_mysql log file.

* The xp_mysql config file is still used and there is no need to
  remove the xp_mysql.dll plugin file (though it will not be used
  by the code anymore).