Add Distance to Table Info

Add distance to table if site coordinates are provided and sort the
table by distance.  If coordinates aren't provided, the column isn't
displayed.
Center "Distance from Site" for Selected Plane

Center "Distance from Site" under "Lat/Long" for selected plane.
Add flightradar24.com link
B"H make sure to close sockets when finished
B"H net_io.c: revert previous change and advertise HTTP 1.1

It seems server code should be compatible with HTTP 1.1; the features
unique to 1.1 mostly are upon the client to support, and some headers
used (for example Cache-Control) may need 1.1.
B"H net_io: http: check if file can be sent
B"H net_io.c: add missing else statement
B"H net_io.c: http serve: return HTTP response codes
B"H net_io.c: use %d like local code
B"H net_io.c: http server: content should be dynamically allocated
B"H net_io.c http server: hopefully mem code is OK now

Still learning the ropes memory-wise :-)
Merge branch 'master' of https://www.github.com/MalcolmRobb/dump1090 into socket_hang
Merge branch 'master' of https://www.github.com/MalcolmRobb/dump1090 into http_server_wk
Change the marker color for aircraft with no recent updates.
B"H Merge branch 'master' of https://www.github.com/MalcolmRobb/dump1090 into socket_hang

Conflicts:
	net_io.c
Merge branch 'master' of https://www.github.com/MalcolmRobb/dump1090 into http_server_wk
Ability to assign bind address for services
Merge pull request #24 from ddeitterick/add_distance_to_table

Add Distance to Table Info
Merge pull request #25 from ddeitterick/center_selected_plane_distance

Center "Distance from Site" for Selected Plane
Merge pull request #30 from tslocum/fr24link

Add flightradar24.com link