JSON Strings and GC Tokens

.. fix json writing so that user metadata no longer conflicts
   with the tokens used by GoldenCheetah, e.g. a user entered
   "NM" in the workout code and that conflicted with the
   token used to delimit a torque value.

.. all user strings are now saved with a space " " appended to
   the value and when read, if there is a trailing space it is
   removed.