Qt5 built in qwt (#570)

- qt4->qt5
- in built qt5 6.1.5 because rhel7 is not upto date with qt5, removed findqwt.cmake
- made a fix in qwt lib (qwt_plot_layout.h) to work with 5.15 and lower versions for qrect constr.
- qt5 forms fixed, qt4 many hard coding forms switched to forms including qtabwidget, scrolls etc, fonts moved to forms
 - docking option enabled by default, removed option to disable docking feature from "Mode"
- added qVersionResolve utility functions to handle compatibility before and after qt5.12
- qtplots (ian's code) takes in gain mode enable to set some settings within the class, with proper gain plot ticks
- ensure gain plots have no zooming of z axis in 2d and y axis in 1d
- removed placeholder text in qpalette in main window form as its not supportd until 5.12 (so using qt5.9 designer insted of qt5.15 to cope)
- tab order
Servers:
- fixed some error messages that were empty for fail in funcs (mostly minor as if this error, major issues)

libs/qwt-6.1.5/include/qwt_spline.h

@@ -0,0 +1,101 @@
+/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
+ * Qwt Widget Library
+ * Copyright (C) 1997   Josef Wilgen
+ * Copyright (C) 2002   Uwe Rathmann
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the Qwt License, Version 1.0
+ *****************************************************************************/
+
+#ifndef QWT_SPLINE_H
+#define QWT_SPLINE_H
+
+#include "qwt_global.h"
+#include <qpolygon.h>
+#include <qvector.h>
+
+/*!
+  \brief A class for spline interpolation
+
+  The QwtSpline class is used for cubical spline interpolation.
+  Two types of splines, natural and periodic, are supported.
+
+  \par Usage:
+  <ol>
+  <li>First call setPoints() to determine the spline coefficients
+      for a tabulated function y(x).
+  <li>After the coefficients have been set up, the interpolated
+      function value for an argument x can be determined by calling
+      QwtSpline::value().
+  </ol>
+
+  \par Example:
+  \code
+#include <qwt_spline.h>
+
+QPolygonF interpolate(const QPolygonF& points, int numValues)
+{
+    QwtSpline spline;
+    if ( !spline.setPoints(points) )
+        return points;
+
+    QPolygonF interpolatedPoints(numValues);
+
+    const double delta =
+        (points[numPoints - 1].x() - points[0].x()) / (points.size() - 1);
+    for(i = 0; i < points.size(); i++)  / interpolate
+    {
+        const double x = points[0].x() + i * delta;
+        interpolatedPoints[i].setX(x);
+        interpolatedPoints[i].setY(spline.value(x));
+    }
+    return interpolatedPoints;
+}
+  \endcode
+*/
+
+class QWT_EXPORT QwtSpline
+{
+public:
+    //! Spline type
+    enum SplineType
+    {
+        //! A natural spline
+        Natural,
+
+        //! A periodic spline
+        Periodic
+    };
+
+    QwtSpline();
+    QwtSpline( const QwtSpline & );
+
+    ~QwtSpline();
+
+    QwtSpline &operator=( const QwtSpline & );
+
+    void setSplineType( SplineType );
+    SplineType splineType() const;
+
+    bool setPoints( const QPolygonF& points );
+    QPolygonF points() const;
+
+    void reset();
+
+    bool isValid() const;
+    double value( double x ) const;
+
+    const QVector<double> &coefficientsA() const;
+    const QVector<double> &coefficientsB() const;
+    const QVector<double> &coefficientsC() const;
+
+protected:
+    bool buildNaturalSpline( const QPolygonF & );
+    bool buildPeriodicSpline( const QPolygonF & );
+
+private:
+    class PrivateData;
+    PrivateData *d_data;
+};
+
+#endif