Add generic templates (#307)

- Add generic full-page templates.  (This feature from 3.4 was missing)
- Also add generic half-page, quarter-page, and envelope templates.
- Add several more common envelope sizes to page-sizes.xml
- Qt print backend does not need pwg_size.
    - Replace with pwg_class, to distinguish between ISO and NA sizes

model/Paper.cpp

@@ -29,12 +29,14 @@ namespace glabels::model
                       const QString& name,
                       Distance       width,
                       Distance       height,
-                      const QString& pwgSize )
+                      const QString& pwgClass,
+                      Type           type )
                 : mId(id),
                   mName(name),
                   mWidth(width),
                   mHeight(height),
-                  mPwgSize(pwgSize)
+                  mPwgClass(pwgClass),
+                  mType(type)
         {
                 // empty
         }
@@ -64,21 +66,27 @@ namespace glabels::model
         }
 
 
-        QString Paper::pwgSize() const
+        QString Paper::pwgClass() const
         {
-                return mPwgSize;
+                return mPwgClass;
+        }
+
+
+        Paper::Type Paper::type() const
+        {
+                return mType;
         }
 
 
         bool Paper::isSizeIso() const
         {
-                return mPwgSize.startsWith( "iso_" );
+                return mPwgClass == "iso";
         }
 
 
         bool Paper::isSizeUs() const
         {
-                return mPwgSize.startsWith( "na_" );
+                return mPwgClass == "na";
         }
 
 }