README update.
DRILL-1411 Fragment memory planning
DRILL-1391 : Fix compilation error in run-time generated code for several math functions over decimal types.
DRILL-1383: Support interpreted execution for Drill expression tree.

Fix OOM while running InterpreterBuilder
Patch for DRILL-705

Currently only supports partitioning/ordering, not yet preceding or
after offsets
DRILL-1386: Push directory filters into group scan for filesystem queries.
DRILL-1414: Move profile storage to DFS rather than using PStore
DRILL-98: MongoDB storage plugin

This commit disables MongoDB PStore due to changes to the PStore interface.
DRILL-1425: Handle unknown operators in web ui
DRILL-1426: Add IO wait stats to HBaseRecordReader
DRILL-1398: Clone HivePartition only when InputSplit has non-null partition in InputSplit->Partition map.
DRILL-1407: Add scan size calculator option to HBase storage plugin configuration
DRILL-1371: HBase queries fail when hbase.scan.sizecalculator.enabled is set to false
DRILL-1419: JSON reader regression from project pushdown patch.

Patch amended to include a minimal subset of the test file needed to confirm the issue.
Drill 1416: convert_from() on JSON fails - regression
DRILL-1125: Apply casts to handle different input types in the join condition
DRILL-1432: Propagate user credentials from client to the fragments
DRILL-1427: Failure to initialize storage plug-in results in complete failure of drill-bit initialization
DRILL-1444: Fix cancel in C++ client library
DRILL-1465: Enhance push partition filter rule to handle Filters appearing above a Project. Modify group scans' digests to include number of files being considered.

Resource files for testing partition filter pushdown.