Refactor attribute action dialog

The attribute action dialog had some UX flaws that an action was edited
in the same dialog as the action list lives. When changing the active
icon without applying changes, all changes have been lost. This fixes
this behavior by using a separate dialog to change action properties.

src/app/CMakeLists.txt

@@ -11,6 +11,7 @@ SET(QGIS_APP_SRCS
   qgsjoindialog.cpp
   qgsannotationwidget.cpp
   qgsattributeactiondialog.cpp
+  qgsattributeactionpropertiesdialog.cpp
   qgsattributetypedialog.cpp
   qgsattributetabledialog.cpp
   qgsbookmarks.cpp
@@ -184,6 +185,7 @@ SET (QGIS_APP_MOC_HDRS
   qgsannotationwidget.h
   qgsapplayertreeviewmenuprovider.h
   qgsattributeactiondialog.h
+  qgsattributeactionpropertiesdialog.h
   qgsattributetypedialog.h
   qgsattributetabledialog.h
   qgsbookmarks.h