DRILL-810 : add isSafe() to Nullable value vector. Check nullable value vector has capacity for new value in run-time code.
setSafe() in variable length vector should check has capacity to hold new value.
Bug fixes in Project operator. Use allocateNewSafe() to allocate space for outgoing batch in Project.

Reenable testcase.
copy unmerged records in merge sort to new buffer
DRILL-802: convert_to(int_field, 'INT_HADOOPV') throws IndexOutOfBoundsException
DRILL-796: Selecting * from HBase tables filtered with 'row_key' returns empty arrays
DRILL-825: MaterializedField is mutable and is not suitable as a KEY in a MAP

+ Minor optimization/cleanup in HBaseRecordReader
DRILL-649: Reading impala and avro generated parquet files

Implemented dictionary encoding for the non-varlength types.
DRILL-816: Fix bug with reading nullable columns resulting in mismatched number of records in vectors.