TAJO-1125: Separate logical plan and optimizer into a maven module.

Closes #210
TAJO-1125: Separate logical plan and optimizer into a maven module. (missed jar copy)
TAJO-1126: Join condition including functions throws IllegalArgumentException.

Closes #209
TAJO-1132: More detailed version info in tsql.

Closes #211
TAJO-1114: Improve ConfVars (SessionVar) to take a validator interface to check its input. (Jihun Kang via hyunsik)

Closes #214
TAJO-1114: Improve ConfVars (SessionVar) to take a validator interface to check its input. (fixed compilation error)
Fixed a missed compilation error in TestValidators.
Revert "Fixed a missed compilation error in TestValidators."

This reverts commit b3749a0931e4e2c5447d9ce4cdfe43245300ef61.
Revert "TAJO-1114: Improve ConfVars (SessionVar) to take a validator interface to check its input. (fixed compilation error)"

This reverts commit 7a65763554e556498b6d52dd2685636c3b6584b3.
Revert "TAJO-1114: Improve ConfVars (SessionVar) to take a validator interface to check its input. (Jihun Kang via hyunsik)"

This reverts commit ee89c65b44142ca640020339e7ab5a608c1a8bf9.
TAJO-1140: Separate TajoClient into fine grained parts.

Closes #213
TAJO-1114: Improve ConfVars (SessionVar) to take a validator interface to check its input. (Jihun Kang via hyunsik)

Closes #218
TAJO-1145: Add 'bin/tajo --help' command. (Jihun Kang via hyunsik)

Closes #220
TAJO-1133: Add 'bin/tajo version' command. (Jihun Kang via hyunsik)

Closes #219
TAJO-1139: ExternalSortExec should delete the intermediate files. (jinho via hyunsik)

Closes #212
TAJO-1141: Refactor the packages hierarchy of tajo-client.

Closes #217
Fixed missed classpath change of TAJO-1141.
TAJO-1150: Some weird methods in QueryClientImpl should be fixed. (Jongyoung Park via hyunsik)

Closes #223
TAJO-1032: Improve TravisCI scripts to adjust log4j log level. (jinho)

Closes #226
TAJO-1153: Merge off-heap package in block_iteration branch to master branch.

Closes #225