aviation_gis_tools: Point given at offset against polar coordinates

Another way of giving location of point of interest in aviation (e. g. obstacles) is providing information about:

• reference point (aerodrome referenc epoint, navaid, runway threshold)
• bearing of reference line (note: it can be given directly or as 'extende line of center line of rwy XX'
• side on which point is located (left, right) against reference line
• offset against reference line