#66 partial implement xorm_cache tag

add Engine.disableGlobalCache and explicit using cache via xorm_cache tag
Merge remote-tracking branch 'origin/master' into feature/cacher-tag
Merge remote-tracking branch 'origin/master' into feature/cacher-tag
Merge remote-tracking branch 'origin/master' into feature/cacher-tag
add Engine.LogSQLQueryTime and Engine.LogSQLExecutionTime for SQL execution time logging
redis cacher implementation, incomplete
Merge remote-tracking branch 'origin/master' into feature/cacher-tag
implemented interface gob encode and decode for redit cacher
resolved merge
code tidy up

logger tidy up

private serialize and deserialize func
Merge remote-tracking branch 'origin/master' into feature/cacher-tag
remove redis_cacher.go
Merge branch 'master' into feature/cacher-tag
add TODO comments
Merge branch 'master' of github.com:go-xorm/xorm
Merge branch 'master' into feature/cacher-tag
update docs/QuickStart.md
changed to cache and nocache tag value support

public Engine.TableInfo() API
resolved merge from origin/master
Merge branch 'feature/cacher-tag'