mel rotomap-edit: toggle follow with 'o'
mel rotomap-edit: toggle follow with 'o'

Allow users to toggle follow mode with the 'o' key in addition to using
a command-line parameter.

Test plan:
$ ./meta/run_tests.sh

.. Exercise 'o' in a rotomap dir ..
.. Exercise --follow in a rotomap dir ..

aevri/mel,aevri/mel