Add support for GPX routes - as a new sublayer type of the now less accurately named...

Add support for GPX routes - as a new sublayer type of the now less accurately named TrackWaypoint layer

Most previous track functionality is made avaliable on this Route type.
Routepoints can have an elevation property.
GPX Routes can be optionally downloaded/uploaded from GPS devices via the Acquire, GPS layer or menu methods.
GPX files with routes may be imported and exported.
Viking .vik files save route and routepoints.

Internally, a route is implemented as a simple boolean flag as part of the track's property.