Remove BlankState menu
UI Nits: default chart fonts smaller

.. the chart labels need to be smaller especially
on small screens, and better to err on the side of
caution and make them smaller.
Let user close blank state

The user can close the blank state screen and
can also click a checkbox to ensure it is not
shown again for this athlete.
Don't export HR if it is zero

Tcx XML HR must be positive, so if there is no
value (i.e. it is zero) then don't write it.

Thanks to Dean Junk for diagnosing this and
posting his findings to them mailing list.
Clear blankstate screen if conditions change

The diary, home and analysis blank state screens will
now close if rides are added.

Still need to make the train view blank state screen
close when devices and workouts are added.
BlankState basics completed

.. now closes train view blankstate when device added
and workouts have been imported.

.. and made the home and diary views have same buttons
as the analysis view. That may change in later releases
when we have planning functions.