an owner for all data files created by cpimport
The patch consists of two parts: cpimport.bin changes, cpimport splitter
changes
cpimport.bin computes uid_t and gid_t early and propagates it down the stack
where MCS creates data files
for extent extention.
Added a getter, moved some methods from protected into public to use
with unit tests, e.g createFile, setPreallocSpace. Added code stub in
FileOp::oid2FileName to use with UT.
Add more comments.
Changed return value for HDFS'es fallocate.
Removed unnecessary code in ColumnBufferCompressed::writeToFile
Replaced Nulls with Empties in variable names.
