Bugs causing it to not be able to un-zoom.

Also, changed an if(true) then true; else false; code
Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

There are many ways of iterating over lists in C++/Qt.
In the specific case of QStrings, it is known [1] that using
foreach with const references avoids the creation of new
QString objects in each iteration, reducing the time consumed
by the loops.

[1] https://blog.qt.io/blog/2009/01/23/iterating-efficiently/Signed-off-by: Anselmo L. S. Melo <anselmo.melo@intel.com>

This makes unit test output easier to read

This makes unit test output easier to read

I was unsure how to update the QwtPlotPrintFilter code, so I just commented it out with a FIXME.

Further consolidation of Plot code into ChartPlot. Also removed some unused variables from LinechartWidget.cc. Also only active curves are recolored in the IncrementalPlot class.

Moved all shared code for IncrementalPlot and LinechartPlot into a common ChartPlot superclass. Also recoloring the background of both widgets now works when switching between color schemes.

Improved line chart, brought back movement on HUD (but still looks somewhat wrong on the dials). Fixed logging for ground time mode

Substantially bugfixed and improved deactivation/activation and persistence of widgets. A lot of testing of Google Earth view, only minor improvements

Significantly improved plotting, now capturing data in linechart allows limmediate processing / analysis of the whole flight

Improved runtime performance, currently hunting down a bug where the whole application gets repainted although only parts of it are refreshed