Move subsurface-core to core and qt-mobile to mobile-widgets

Having subsurface-core as a directory name really messes with
autocomplete and is obviously redundant. Simmilarly, qt-mobile caused an
autocomplete conflict and also was inconsistent with the desktop-widget
name for the directory containing the "other" UI.

And while cleaning up the resulting change in the path name for include
files, I decided to clean up those even more to make them consistent
overall.

This could have been handled in more commits, but since this requires a
make clean before the build, it seemed more sensible to do it all in one.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/metrics.h

@@ -0,0 +1,36 @@
+/*
+ * 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
+	// devicePixelRatio
+	double dpr; // 1.0 for traditional screens, HiDPI screens up to 3.0
+	IconMetrics();
+};
+
+const IconMetrics & defaultIconMetrics();
+void updateDevicePixelRatio(double dpr);
+
+#endif // METRICS_H