Progress!

Masked error caused by saving dbc while editor is open that causes
msg IDs to go crazy by making editor modal, but that affects all
other windows, so might be a better fix.

Added new value type of VALUE_STRING, probably better named
ENUMERATED_STRING, and it uses the table in the editor to define
the enum.

Fixed a bug in the signal viewer load when a signal is not matched
(I found it by renaming a signal and then loading)

signalviewerwindow.cpp

@@ -286,13 +286,14 @@ void SignalViewerWindow::loadDefinitions(bool append)
                     if (msg  = dbcHandler->findMessage(msgName))
                     {
                         sig = msg->sigHandler->findSignalByName(sigName);
-                        loadedSignals.append(sig);
+                        if(sig)
+                            loadedSignals.append(sig);
                     }
                     else  if(msg = dbcHandler->findMessage(msgId))
                     {
                         sig = msg->sigHandler->findSignalByName(sigName);
-                        //fix anything up about the name?
-                        loadedSignals.append(sig);
+                        if(sig)
+                            loadedSignals.append(sig);
                     }
                     else
                     {