fix: avoid create menu actions everytime when trigger context menu.

fix the minor memory leak issue, also bring some possibility to
implement custom keybinding.

And oops I also did another feature in this commit..
Now we are able to set mouse wheel behavior in config dialog.

CMakeLists.txt

@@ -30,6 +30,7 @@ set (PPIC_CPP_FILES
     app/main.cpp
     app/framelesswindow.cpp
     app/mainwindow.cpp
+    app/actionmanager.cpp
     app/graphicsview.cpp
     app/graphicsscene.cpp
     app/bottombuttongroup.cpp
@@ -47,6 +48,7 @@ set (PPIC_CPP_FILES
 set (PPIC_HEADER_FILES
     app/framelesswindow.h
     app/mainwindow.h
+    app/actionmanager.h
     app/graphicsview.h
     app/graphicsscene.h
     app/bottombuttongroup.h