Samples added to openslide-testdata repository

[Benjamin Gilbert]

Hi all,

A number of new scans have been added to openslide-testdata:

- Hamamatsu NDPI: newer files with a slightly different structure
- Mirax: BMP- and PNG-encoded slides, and fluorescence samples with 
CURRENT_SLIDE_VERSION = 2
- Olympus VSI
- Ventana BIF
- Zeiss ZVI: mosaic images

As always, they're available from:

     http://openslide.cs.cmu.edu/download/openslide-testdata/

We are always looking for more sample data!  The wishlist is on the wiki:

     https://github.com/openslide/openslide/wiki/DesiredTestData

At the moment, we're particularly interested in:

- Leica SCN with multiple main image pyramids
- Sakura SVSLIDE
- Ventana BIF with multiple scan regions

If you are able to contribute scans in any of these formats, and 
especially if you can do a bit of paperwork permitting us to 
redistribute the scan data, please contact me off-list.

Thanks,
--Benjamin Gilbert