Image to Tiles feedback

[Rangi42]

• [x] Default the Palette checkbox to on
• [ ] Warn if a generated tilemap+tileset did not have a palette and has more colors that the platform format supports (e.g. 4 for GBC)
• [x] In the Saved dialog, mention both the .tilemap and .attrmap files if both exist
• [x] Save the last selected formats as defaults for the next run

[Rangi42]

(If the user does not choose the create a palette, presumably they know what they're doing. Maybe the generated tileset is just for a mockup; maybe they plan to flatten its colors on their own; maybe they have some hardware tricks in mind to use all the colors; etc. A warning that there are "too many colors" only makes sense in the context of Tilemap Studio generating a palette itself, since it tries to pack the colors into the format's available palettes. It would also be vulnerable to false negatives: six unique colors, where each tile only uses four at a time, may not be doable on the GBC if tiles use more than 8 of the 15 possible 4-color combinations.)