Fix for panasonic

Version 1.6.28 (#17)

* Fix perf for dng

* Fix nikon Preview

* Add doc

* Fix Nikon preview

* Fix

* Fix raw decoder

* New version

* Add a donate button

* Small imporovement for low memory device

* Change app name

* Clean up

* Fix a null exception

* Quick fix fo demosaic

* First fix for RW2

* Add support for RAW2 thumbnail

* Clean up

* Clean up for RAW v1

* Fix for Nikon d2x (white balance still not correct)

* Update nuget packages