Partial fix for #228: ambiguous navaid-names

Partial fix for #228: ambiguous navaid-names

This fixes at least the startup process.
If an ambigous fix name was presented with --vor=ID or --ndb=ID
present a list of matching records along with frequency and
position in the console to give the user the chance to pick
the correct one by adding the frequency with --vor-frequency=nnn.nn

It does not yes solve the issue when the user relocates using the
GUI dialog. This requires some GUI and Nasal hacking along with a
new Nasal helper function "navaidinfo".