Big-Ugly Style Update (#278)

* Bulk replaced tabs with spaces
* Bulk removed trailing whitespace from lines
* Replaced c-style comments with c++-style comments in file banners
* Replace nested namespace definitions with single concise definitions (C++17), this keeps the indentation more manageable
* Cleanup ordering and spacing of include directives
* Bulk renaming of header file extensions from '.h' to '.hpp'.
* Update CODING-STYLE.md
* Update target_compile_features from cxx_std_11 to cxx_std_20.
* Refresh .clang-format file.  Still needs a lot of tweaking.

glabels/ui/EditVariableDialog.ui

@@ -126,7 +126,7 @@
   <customwidget>
    <class>glabels::ColorButton</class>
    <extends>QPushButton</extends>
-   <header>ColorButton.h</header>
+   <header>ColorButton.hpp</header>
    <slots>
     <signal>colorChanged()</signal>
    </slots>

glabels/ui/ObjectEditor.ui

@@ -1515,7 +1515,7 @@
   <customwidget>
    <class>glabels::ColorButton</class>
    <extends>QPushButton</extends>
-   <header>ColorButton.h</header>
+   <header>ColorButton.hpp</header>
    <slots>
     <signal>colorChanged()</signal>
    </slots>
@@ -1523,7 +1523,7 @@
   <customwidget>
    <class>glabels::BarcodeMenuButton</class>
    <extends>QPushButton</extends>
-   <header>BarcodeMenuButton.h</header>
+   <header>BarcodeMenuButton.hpp</header>
    <slots>
     <signal>selectionChanged()</signal>
    </slots>
@@ -1531,7 +1531,7 @@
   <customwidget>
    <class>glabels::FieldButton</class>
    <extends>QPushButton</extends>
-   <header>FieldButton.h</header>
+   <header>FieldButton.hpp</header>
    <slots>
     <signal>keySelected(QString)</signal>
    </slots>

glabels/ui/PrintView.ui

@@ -665,7 +665,7 @@
   <customwidget>
    <class>glabels::Preview</class>
    <extends>QWidget</extends>
-   <header>Preview.h</header>
+   <header>Preview.hpp</header>
    <container>1</container>
   </customwidget>
  </customwidgets>

glabels/ui/PropertiesView.ui

@@ -431,7 +431,7 @@
   <customwidget>
    <class>glabels::SimplePreview</class>
    <extends>QGraphicsView</extends>
-   <header>SimplePreview.h</header>
+   <header>SimplePreview.hpp</header>
   </customwidget>
  </customwidgets>
  <resources>

glabels/ui/SelectProductDialog.ui

@@ -530,12 +530,12 @@
   <customwidget>
    <class>glabels::TemplatePicker</class>
    <extends>QListWidget</extends>
-   <header>TemplatePicker.h</header>
+   <header>TemplatePicker.hpp</header>
   </customwidget>
   <customwidget>
    <class>glabels::SimplePreview</class>
    <extends>QGraphicsView</extends>
-   <header>SimplePreview.h</header>
+   <header>SimplePreview.hpp</header>
   </customwidget>
  </customwidgets>
  <resources>

glabels/ui/TemplateDesignerOneLayoutPage.ui

@@ -207,7 +207,7 @@
   <customwidget>
    <class>glabels::SimplePreview</class>
    <extends>QGraphicsView</extends>
-   <header>SimplePreview.h</header>
+   <header>SimplePreview.hpp</header>
   </customwidget>
  </customwidgets>
  <resources>

glabels/ui/TemplateDesignerTwoLayoutPage.ui

@@ -245,7 +245,7 @@
   <customwidget>
    <class>glabels::SimplePreview</class>
    <extends>QGraphicsView</extends>
-   <header>SimplePreview.h</header>
+   <header>SimplePreview.hpp</header>
   </customwidget>
  </customwidgets>
  <resources>