Add initial planning for paths API

The idea is to reduce manual string directories in the general code as
much as possible, in order to reduce typos and general weirdness.

src/utils/paths.h

@@ -0,0 +1,25 @@
+#pragma once
+#include <string>
+#include <optional>
+
+namespace paths
+{
+using std::optional;
+using std::string;
+
+optional<string> binaryDirectory();
+optional<string> binaryDirectoryFindFile( string fileName );
+
+optional<string> qmlDirectory();
+optional<string> qmlDirectoryFindFile( string fileName );
+
+optional<string> imageDirectory();
+optional<string> imageDirectoryFindFile( string fileName );
+
+optional<string> soundDirectory();
+optional<string> soundDirectoryFindFile( string fileName );
+
+optional<string> settingsDirectory();
+optional<string> settingsDirectoryFindFile( string fileName );
+
+} // namespace paths