Implement drift time to distance maps.
Not actually used.
To find the drift map parameters, the drift chamber plane names had to be
changed from 1-12 to 1x1, 1y1, ...
This meant that the root tree names changed too.
The determination of 1x1, 1y1 names etc is just a hack.  It should ultimately
be derived from the wire angles, or we should do away with such names.