Merge in the GPS tracking branch

[mvl22]

The Hackney app branch contains the GPS tracking facility.

For various reasons, it would good if this functionality were available in the main app.

So the action here is to rework the GPS facility so that it is available as a single menu item, then merge it into the main app.

[neilkachu]

I'll need a bit more detail on this, these routes are not CS routes (I did mention this should be considered when we started Hackney) so they aren't part of the main data set. For me this is all tied up the need for a proper user account.