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)

slsDetectorGui/include/qDefs.h

@@ -41,7 +41,10 @@ class qDefs : public QWidget {
      */
     qDefs(){};
 
-    static const int Q_FONT_SIZE = 9;
+    static QFont GetDefaultFont() {
+        return QFont("Cantarell", 10, QFont::Normal);
+    }
+
     static const int DATA_GAIN_PLOT_RATIO = 5;
     static const int MIN_HEIGHT_GAIN_PLOT_1D = 75;
     static const int GUI_ZMQ_RCV_HWM = 2;