refs #538, Formatting, minor tweaks, comments

* new slot syntax in ATC station component
* formatting, comments
* tab order
* utility function for severity in status message
* null checks in threadutils
* invalidKey function in datastore
* changed data object keys (cached objets)
* added missing value object compare cases
* renamed timer in context network
* finder function for model list
* renamed getContainer to container (as it is just a reference)

src/blackmisc/datastore.h

@@ -49,6 +49,9 @@ namespace BlackMisc
         //! Has valid DB key
         bool hasValidDbKey() const { return m_dbKey >= 0; }
 
+        //! Invalid key
+        static int invalidDbKey() { return -1; }
+
     protected:
         //! Constructor
         IDatastoreObjectWithIntegerKey() {}
@@ -98,6 +101,9 @@ namespace BlackMisc
         //! Has valid DB key
         bool hasValidDbKey() const { return !m_dbKey.isEmpty(); }
 
+        //! Invalid key
+        static QString invalidDbKey() { return ""; }
+
     protected:
         //! Constructor
         IDatastoreObjectWithStringKey() {}