DRILL-656: Fix for test case failure in TestPoolChunkTrim
DRILL-633: Fix toString() for DrillFuncHolder and few other types.

 - Added o.a.d.common.types.Types.toString(MajorType) method to convert a MajorType to string without the line breaks.
 - Log a trace message with all registered Drill functions.
DRILL-654: Fix for MaterializedField.getAsSchemaPath()
DRILL-655: Miscellaneous fixes for SchemaPath

 - Fixed equals() and hashCode().
 - Made PathSegment immutable outside of package.
 - Made ArraySegment and NameSegment final.
DRILL-664: Improve Rpc error message display
DRILL-626: Project push down into HBase scan
Improve HBase test cases.