Translation Enablement & consider "seconds" translation

... multiple tr() added for Intervals. Compare Pane
... in Compare Pane - in time metrics check for both "seconds" and
translated tr(seconds) (following the concept for time as at most other
places where units == "seconds" are checked

(cherry picked from commit 6c78b00b65a1d794eb99038f21d6e705d119d29e)
Translation for Filter/Autofilter

... Filter/Autofilter did not consider Translation of the Filter
Criteria - using Special Fields (to translate from internal to external
names is working for me - but do special fields cover all variants?)

(cherry picked from commit 5cc4218a2a0877a1f8ff4f36d1367bee37c34d2d)
Calendar Chart now honours colour preferences

.. think that is the last of all the charts now done.
No smoothing applied when smooth < recIntSecs

.. its pointless

.. it is a big performance overhead

Fixes #753.
Turn smoothing OFF if smooth < recIntSecs

.. i.e. don't do ANY smoothing

.. last commit fixed performance but really adds
   no value to smooth data to the interval it was
   recorded at !!
Don't allow 0 smoothing in compare mode

.. we need all intervals to have a common smoothing
   applied or it breaks the charts
Merge pull request #903 from Joern-R/pull1

Translation Enablement & consider "seconds" translation
Fix time tooltip on AllPlot
Fix useMetric in Scatter plot

.. was broken when we moved useMetricUnits to the
   Athlete class and a local bool remained.
Merge remote-tracking branch 'upstream/master'