BlankState: Minor cosmetics

.. changed the image to be fainter and smaller
.. the text to be larger and bolder
UI Nits: PfPvWindow double click to change quarters (CP and cadence)
PfPvWindow : Double Click
Update edit values for CP et CAD after double click
BlankState: Analysis view more blanks

- Better handling of a NULL ride for most of the analysis charts
- Don't show activity editor if no data rows to edit
BlankState: Cosmetics

Just changed the icon for add device and tidied up
the icon sizing and button sizing a smidge. As ever,
tastes vary.