DRILL-1634: Fix issue in complex type expression type resolution, when Drill queries a nested array.

code clean up.
DRILL-1544 : Support escape character in "like" or "similar to" SQL operator.

Conflicts:
	exec/java-exec/src/test/java/org/apache/drill/TestExampleQueries.java
DRILL-1592: Detect drillbit failure and cancel the affected running queries.

Revise code based on review comments.
Revise code based on comments: only track the newly dead drillbits.