flight.js: remove unneccessary .show() and .hide() when adding/removing a plane marker
flight.js: don't recreate the plane icons on every update
flight.js: clone point for plane icon

Otherwise moving the plane icon changes the linestring itself.
flight.js: use ol.LonLat instead of ol.Point for transformation

LonLat is more lightweight...
setup.py: update Flask-WTF to 0.9.5

Fixes a bug with the new released WTForms 2.0 which doesn't
work with Flask-WTF 0.9.x
templates/tracking/info: update webserver URL

Fixes #318
livetrack24: store terrain elevation of fix

Fixes #269