This fixes #265.

After spending some time on this and ending up trying various ideas, this ended up being what I thought was the best and simplest solution. Basically, when write_tile_cfg is called, loop through the zones in self.v_["zone_list"] and compare each zone with the active tile coordinates. If any point (lat, lon) in each zone matches, then we append that to a new tile_zones list which is then saved to the tile configuration. For future reference (mostly for myself), here's some more details:

• self.v_["zone_list"] is a tk.StringVar and has to be converted to a Python string
• The string is then converted to a list so it can be iterated
• Convert zone_list to a set for optimization (faster and removes any duplicate coordinates within a zone)
• Check if the active coords (longitude + 1 since the active coordinates are based on the SW corner) are in the set
• Finally, write the matching zones to the configuration file

Changes:

• When write_tile_cfg is called, only save zones for the selected/active tile.
• Clean up some cfg_vars descriptions for consistency.
• Added feedback (console output) when configuration window buttons (Load Tile Config, Write Tile Config, etc.) are used.

The bottom two are obviously just clean up and personal preference, but I thought it was a simple but helpful change.