Add JNX Support.

[ninsbl]

An interesting hint from Mike on JNX format:

"The KMZ Format is very slow. So if you want to show maps its cool to use JNX format.

Todo this A. Whiter added a Firmware Patch and also has some Format Information about JNX.

Actually I can download WMS Tiles using Mobile Atlas Creator and use tools to convert it to JNX.

Last but not least you could create IMG files, but the easiest way would to create JNX Files.
Also note: If you load the JNX Files to your Garmin, you can see it in the Basecamp Software, too!
Very cool."

A high resolution map canvas export (to GeoTIFF) could be easily converted to JNX using mklandkarte