logic: Application settings migration system

* Added version number to ApplicationSettings
* Added SettingsMigrator for defining migration rules for different ApplicationSettings versions
* Migrate ApplicationSettings when loading

src/lib/utility/ConfigManager.cpp

@@ -220,6 +220,11 @@ void ConfigManager::setValues(const std::string& key, const std::vector<bool>& v
 	setValues(key, stringValues);
 }
 
+void ConfigManager::removeValues(const std::string& key)
+{
+	m_values.erase(key);
+}
+
 bool ConfigManager::isValueDefined(const std::string& key) const
 {
 	std::multimap<std::string, std::string>::const_iterator it = m_values.find(key);

src/lib/utility/ConfigManager.h

@@ -38,6 +38,8 @@ public:
 	void setValues(const std::string& key, const std::vector<float>& values);
 	void setValues(const std::string& key, const std::vector<bool>& values);
 
+	void removeValues(const std::string& key);
+
 	bool isValueDefined(const std::string& key) const;
 
 	bool load(const std::shared_ptr<TextAccess> textAccess);