TAJO-1099: LogicalPlanner::convertDataType causes NPE in some cases.

Closes #185
TAJO-1104: Using asterisk with GROUP BY causes NPE.

Closes #187
TAJO-1021: Remove the member variable Builder from all classes inherited from ProtoObject.

Closes #188
TAJO-1106: Missing session check in getFinishedQuery API. (Yongjun Park via hyunsik)

Closes #190
TAJO-1093: DateTimeFormat.to_char() is slower than SimpleDateFormat.format(). (bug fix)

Closes #194
TAJO-1069: TAJO-1069: Add document to explain High Availability support. (jaehwa)

Closes #180
TAJO-1105: Add thread which detects JVM pauses like HADOOP's. (jinho)

Closes #191
TAJO-1107: Broadcast join on non-leaf node scans only first data file.

Closes #193
TAJO-1110: JAVA_PULLSERVER_HEAP_MAX in bin/tajo should be increased.

Closes #197
Update Apache POM to 15.
TAJO-1111: TestKillQuery.testKillQueryFromInitState occasionally fails.

Closes #198
TAJO-1113: SubQuery in KILLED state should handle unexpected events.

Closes #199
[maven-release-plugin] prepare release release-0.9.0-rc0
[maven-release-plugin] prepare for next development iteration
Change the pom version of tajo-hcatalog to 0.9.1-SNAPSHOT.