OmeroCpp: Add .exe as an executable extension only on Windows
Merge pull request #649 from rleigh-dundee/cpp-exeext

OmeroCpp: Add .exe as an executable extension only on Windows
Draft of incomplete code for rewriting path names.
Expect path-fixer bean and test actual usability of safe filepaths.
Bug-fixes to cover Windows better.
Expand path sanitization testing.
Add tests, Leica OME filename test, too-similar paths detection.
Add more unit tests.
Fix whitespace in new classes.
Added FsFile concatenator and unit test for FsFile constructors.
Add file path sanitizer as Spring bean.
Refactor server- and client-side path transformation into separate classes.
Move all FSlite unit tests into the same package.
Integrate FsFile into existing repository code.
Rewrite suggestOnConflict to use FsFile more and sanitize paths.
Adjust code in light of latest import destination path discussion.
Zero-pad day and month in repository path template expansion.
Calculate checksums for imported images

The checksum algorithm has been changed from SHA-1 to Adler32
(with the possibility of further extension). The new faster algo
calculates values, that are then stored in the Pixels table.
Changes have been implemented both client- and server-side.