User Table Scan
添加了对segment和join pop的支持
Merge remote-tracking branch 'origin/i20' into i16
hbaseUserScanEntry
Merge remote-tracking branch 'origin/i20' into i16
HbaseEventScanEntry and HbaseUserScanEntry extends HbaseScanEntry
添加了对segment和join pop的支持
hbaseScanPOP ScanEntry : EventScanEntry+UserScanEntry
Merge remote-tracking branch 'origin/i20' into i16

Conflicts:
	sandbox/prototype/exec/java-exec/src/main/java/org/apache/drill/exec/opt/BasicOptimizer.java
Merge remote-tracking branch 'origin/i20' into i16
add interface for user table scan without property value
Merge remote-tracking branch 'origin/i20' into i16

Conflicts:
	sandbox/prototype/exec/java-exec/src/main/java/org/apache/drill/exec/opt/BasicOptimizer.java
Merge remote-tracking branch 'origin/i20' into i16
不带用户群的功能