TAJO-949: PullServer does not release files, when a channel throws an internal exception. (jinho)

Closes #76
TAJO-995: HiveMetaStoreClient wrapper should retry the connection
TAJO-990: Implement a tool to find tajo configurations. (jaehwa)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo
TAJO-996: Sometimes, scheduleFetchesByEvenDistributedVolumes loses some FetchImpls.

Closes #109
TAJO-994: 'count(distinct x)' function counts first null value.

Closes #106
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo
TAJO-999: SequenceFile key class need to be compatible. (jaehwa)

Closes #110
TAJO-928: Session variables should override query configs in TajoConf.

Closes #98
TAJO-947: ColPartitionStoreExec can cause URISyntaxException due to special characters. (Mai Hai Thanh via hyunsik)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo