DRILL-918: During Sort, handle the case where the child SelectionVector produces 0 records.
DRILL-799: Use static constants instead of Math.pow() to compute powers of 10 while adjusting scale of decimal data type.
DRILL-913: Fix IOOB in HashJoinProbe when input is empty batch
Update trim so that it synchronized within the arena to avoid inconsistent state.
DRILL-887: TestQueriesOnLargeFile.testMergingReceiver fails on Windows
Enable View persistence, Storage Plugin and System option persistence.

Conflicts:
	exec/java-exec/src/main/java/org/apache/drill/exec/ExecConstants.java
	exec/java-exec/src/test/java/org/apache/drill/exec/cache/TestCacheSerialization.java
Adding HBase Persistent Store.

+ Modified some interfaces and configuration keys.

Conflicts:
	exec/java-exec/src/main/java/org/apache/drill/exec/ExecConstants.java
Delete views after test and close ResultSet objects after use
Enable editing of storage plugin via http
DRILL-909: TestSimpleExternalSort.outOfMemoryExternalSort() hangs with use of UnlimitedRawBatchBuffer

- *Not a fix*. Disabling the failing test until a fix is checked in.
Added date/time functions: age, transaction_timestamp and statement_timestamp; math functions: lshift and rshift.
Add Web UIs using templates.

* Added GUI to storage.
* Query submission and sorted results.
Drill configuration changes

+ Moved bootstrap-storage-plugins.json from "conf/" to "java-exec" jar.
+ Cleared drill-override.conf and added drill-override-example.conf
+ Updated maven assembly descriptor.