* Introduce TAppSettings, created in dpr file
* Implement read and write methods, and replace callers of GetRegValue and MainReg.WriteInt/... with these
* Optimize read and write methods for avoiding redundant accesses to registry
* Auto-remove stored default settings from registry to avoid registry spam
* Replace synced MainForm.pref* variables with TAppSettings.Read* calls
* Move SetLocales call to dpr file
* Move MainForm.FDirname* variables to appropriate methods in helpers.pas
* Implement TQueryHistory.Create(SessionPath), reading its items within constructor
