Rework pkg/log, add 'loglevel' and 'logdate' flags, streamline

- removes some previously added manual location strings: now handled by pkg/log depending on loglevel
- kept manual string locations on fmt print functions
- add 'notice' and 'critical' loglevels
- add 'Panic' and 'Panicf' functions to log panics
- adresses issue #26

internal/repository/user.go

@@ -42,12 +42,12 @@ func GetUserCfgRepo() *UserCfgRepo {
 			FOREIGN KEY (username) REFERENCES user (username) ON DELETE CASCADE ON UPDATE NO ACTION);`)
 
 		if err != nil {
-			log.Fatalf("REPOSITORY/USER > db.DB.exec() error: %v", err)
+			log.Fatalf("db.DB.exec() error: %v", err)
 		}
 
 		lookupConfigStmt, err := db.DB.Preparex(`SELECT confkey, value FROM configuration WHERE configuration.username = ?`)
 		if err != nil {
-			log.Fatalf("REPOSITORY/USER > db.DB.Preparex() error: %v", err)
+			log.Fatalf("db.DB.Preparex() error: %v", err)
 		}
 
 		userCfgRepoInstance = &UserCfgRepo{