implement physical operator segment
Merge remote-tracking branch 'origin/i20' into i20
HbaseUserScanPOP
Merge remote-tracking branch 'origin/i20' into i20
UserScanPOP entry  creator
Merge remote-tracking branch 'origin/i20' into i20
test join , group by , aggregate together
hbase recordreader recordSet+2>capacity
.
change TableScanner using cache and batch in scan
 fix conflict
fix aggr bugs
add physical_test4
Merge remote-tracking branch 'origin/i20' into i16
删除了没用的Groupby类, 增添了min5和普通查询的测试用例.