TAJO-1172: Remove Trevni storage type and its related classes (DaeMyung Kang via hyunsik)

Closes #244
TAJO-1184: Upgrade netty-buffer to 4.0.24.Final. (jinho)

Closes #248
Merge branch 'master' of http://git-wip-us.apache.org/repos/asf/tajo into index_support
Merge branch 'index_support' of http://git-wip-us.apache.org/repos/asf/tajo into index_support