mode: move responsabilities from mode to modehandler

- Pass the following responsabilities from mode to mode handler:
   - active / deactive target mode
   - get active mode
   - create new modes

- Move back setting averaging mode when settings are
updated using getModes() method instead of handling
logic in mode handler.

Software/PC_Application/Generator/generator.cpp

@@ -1,4 +1,5 @@
 #include "generator.h"
+#include "modehandler.h"
 
 #include <QSettings>
 
@@ -55,7 +56,7 @@ void Generator::fromJSON(nlohmann::json j)
 
 void Generator::updateDevice()
 {
-    if(!window->getDevice() || Mode::getActiveMode() != this) {
+    if(!window->getDevice() || window->getModeHandler()->getActiveMode() != this) {
         // can't update if not connected
         return;
     }