Move qt-ui to desktop-widgets

Since we have now destkop and mobile versions, 'qt-ui' was a very
poor name choice for a folder that contains only destkop-enabled
widgets.

Also, move the graphicsview-common.h/cpp to subsurface-core because
it doesn't depend on qgraphicsview, it merely implements all the
colors that we use throughout Subsurface, and we will use colors on both
desktop and mobile versions

Same thing applies for metrics.h/cpp

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

subsurface-core/metrics.h

@@ -0,0 +1,32 @@
+/*
+ * metrics.h
+ *
+ * header file for common function to find/compute essential UI metrics
+ * (font properties, icon sizes, etc)
+ *
+ */
+#ifndef METRICS_H
+#define METRICS_H
+
+#include <QFont>
+#include <QFontMetrics>
+#include <QSize>
+
+QFont defaultModelFont();
+QFontMetrics defaultModelFontMetrics();
+
+// Collection of icon/picture sizes and other metrics, resolution independent
+struct IconMetrics {
+	// icon sizes
+	int sz_small; // ex 16px
+	int sz_med; // ex 24px
+	int sz_big; // ex 32px
+	// picture size
+	int sz_pic; // ex 128px
+	// icon spacing
+	int spacing; // ex 2px
+};
+
+const IconMetrics & defaultIconMetrics();
+
+#endif // METRICS_H