Added "Antenna Coverage"-tab to Settings-dialog
Values are changed but not saved yet.
'antennaBaseCoverage.txt'-file can be downloaded and saved to 'public_html'-directory. File is read on 'initialize()'-function if client browser does not have at least 3/4 of coverage data.
'dump1090.c'-file has now txt and png mime-types.

	modified:   .gitignore
	modified:   dump1090.c
	new file:   public_html/3rdparty/FileSaver.js
	modified:   public_html/config.js
	modified:   public_html/gmap.html
	modified:   public_html/options.js
	modified:   public_html/script.js