PCX Plugin Updated

As mentioned here I created a PCX file type plugin for Paint.NET

In response to a request from a user who needed to preserve the palette during load/save cycles (some downstream process required that the palette remain fixed) I updated the code and save dialog with a new checkbox: Use original palette. If checked, and if the document was originally loaded as a PCX (or as a PCX and saved as a PDN file, I think) then it will re-save using the original palette.