private Engine.LogSQL and create ILogger interface that is compatible wi...

private Engine.LogSQL and create ILogger interface that is compatible with log/syslog package. Also fixed use of LogError instead of LogSQL

sample output:
[xorm] 2014/02/12 01:28:20.782647 [info] [sql] SELECT `ProcessorsStruct`.`Id` FROM  `ProcessorsStruct` WHERE `Id`=? LIMIT 1 [args] [[1]]