logic: paths in ProjectSettings relative to file not working directory

This change checks all paths in the ProjectSettings file for relativity and makes them relative to the location of the
ProjectSettings file if necessary. The paths are also correctly saved relative to the file.

src/lib/settings/ApplicationSettings.h

@@ -3,10 +3,10 @@
 
 #include <memory>
 
-#include "settings/CommonSettings.h"
+#include "settings/Settings.h"
 
 class ApplicationSettings
-	: public CommonSettings
+	: public Settings
 {
 public:
 	static std::shared_ptr<ApplicationSettings> getInstance();
@@ -14,6 +14,11 @@ public:
 
 	std::string getStartupProjectFilePath() const;
 
+	// source
+	std::vector<FilePath> getHeaderSearchPaths() const;
+	std::vector<FilePath> getFrameworkSearchPaths() const;
+	std::vector<std::string> getCompilerFlags() const;
+
 	// application
 	std::string getFontName() const;
 	void setFontName(const std::string& fontName);