make code compile on windows

switched unix-specific (also jmv specific) uid/gid detection to reflection.
Merge pull request #18 from radai-rosenblatt/master

make code compile on windows
refactor-out timestamp conversion code, allow for millisecond accuracy
Merge pull request #19 from radai-rosenblatt/master

refactor-out timestamp conversion code, allow for millisecond accuracy
make Stat Cloneable
Merge pull request #20 from radai-rosenblatt/master

make Stat Cloneable
calculate index in the FsExport constructor

While debugging slow NFS performance accompanied by high CPU usage noticed that FsExport.getIndex() determines some index on every call from what seems like immutable data. Moved it to constructor.

Target: master
Request: 0.7
Acked-by: Paul Millar <paul.millar@desy.de> Albert Rossi <arossi@fnal.gov>
Patch: https://rb.dcache.org/r/7372/