Merge pull request #510 from rleigh-dundee/cellomics-location-perf-develop

CellomicsReader: Improve performance of initFile (develop)
ScanR: clear the pixel buffer when an invalid TIFF is found
merge develop -D org -I include -E exclude: PR 506 (Memoizer: use Location instead of File to represent 'id')
merge develop -D org -I include -E exclude: PR 512 (xsd-fu: Extend C++ support to generate headers and include guards)
merge develop -D org -I include -E exclude: PR 518 (ScanR: clear the pixel buffer when an invalid TIFF is found (rebased onto develop))