BETA - Major Update

Changes:
#1. Uses zip format for downloads to improve speed.
#2. Ability to download surrounding charts as well as the selected area.
#3. 64bit Windows problem still needs to be resolved.
#4. Option to delete the last file(s) downloaded. Allows changing satellite source for the charts.
#5. Area for selection better highlighted.
#6. Surrounding charts cannot be downloaded if zoom level less than 12 i.e. very small scale.
#7. Direction arrows to move to adjoining area for download. May not work on Linux.
NOTE: Press 'O' to release the box.
#8. Selection box changes in size to reflect size of satchart that will be downloaded.

TODO: Extensive testing on Linux.