Add distance information to DX exports

[Ed McDonagh]

As reported by @hrkhosravi there are no distances currently being indluded it the DX exports.

[Ed McDonagh]

Attempt to address ref #242 and #243

→ <<cset a0ff9d777395>>

[Ed McDonagh]

I've tested this @hrkhosravi and it seems to work. Can you try replacing your dx.py and dx_export.py files with the ones in these commits and test it please. You'll need to restart Celery, and I've only looked at the Excel export, not csv.

[Ed McDonagh]

Attaching modified version of dx_export.py

[Ed McDonagh]

Merging the distance measurements corrections and enhancements, closes issue #242 and #243

→ <<cset dd991dd3c399>>