Core/DB Layer: - Fix "Thread #1 unlocked a not-locked lock at 0x6D56E90" helgrind error (thanks to Aokromes for logs). Cause was unlocking MySQL connection on shutdown, but concurrent access at this point is not required.

- Remove redundant locking in PingOperation. Since these are delayed to async threads with their own MySQL connection, no concurrent access here either.
- Codestyle cleanup
- Documentation refining

src/server/shared/Database/MySQLConnection.cpp

@@ -58,17 +58,13 @@ MySQLConnection::~MySQLConnection()
 {
     ASSERT (m_Mysql); /// MySQL context must be present at this point
 
-    sLog->outSQLDriver("MySQLConnection::~MySQLConnection()");
     for (size_t i = 0; i < m_stmts.size(); ++i)
         delete m_stmts[i];
 
     for (PreparedStatementMap::const_iterator itr = m_queries.begin(); itr != m_queries.end(); ++itr)
-    {
         free((void *)m_queries[itr->first].first);
-    }
 
     mysql_close(m_Mysql);
-    Unlock();   /// Unlock while we die, how ironic
 }
 
 void MySQLConnection::Close()