0.17.2 - a bugfix update

I found the time to clean up some loose threads, deal with 2 reported bugs, and combing through the code i found and fixed some more.

Won't be making a video this time since the update is relatively small, but here's some key notes in order of importance:

• Save/open binary actions have been collected in the File menu. If you prefer the old, classic organization, you can switch in the Preferences.
• Dragging a single tile to swap it should now work as expected regardless context.
• It's now possible to set the "null tile" to the current tile by double clicking on the null tile bevel. 
• Nudging sprites by arrow keys should now work as expected even while "snap" is on.
• Screen/map box-selections are retained even if clicking to select another tile on the tileset. If you wish to force deselection, hold shift or ctrl while doing so (this signals the start of a new box- or multi selection; respectively).
• "Select All" is now more context aware / less fiddly. Additionally, repeated presses toggles between selecting all of a screen and all of a full map.
• It's now possible to toggle Navigator zoom to 200%. Hold Shift and double click. This can be useful on 4k screens with no scaling.

For more details on these and other minor changes, please view the changelog attached in the zip file.