Similar to other DPs, it is what the users expect and it is easier
to try with different parameters.
When called automatically existing watts are preserved
to avoid accidental overwrite.
This patch closes#2216 which incorrectly prompts for 'Wind Heading
(origin)' when estimating power. The correct term for origin of wind is
'Wind Direction'.
.. a data processor can now be configured to run on save
.. in addition, the data processor is now passed the operation
that is triggering it: "Manual", "ADD", "UPDATE", "DELETE",
"IMPORT".
.. a new data processor has been added to write a JSON file to
the snippet directory (added to the athlete structure).
.. this is so we can output a snippet every time an activity is
added, updated or deleted (i.e. runs "on save").
.. these JSON snippets can be used to update external datastores
where coaches use other analytic software but don't want to
manually sync GC changes with there external stores.
