check for new version rework, support "check for stable updates only" mode

src/slic3r/GUI/ReleaseNote.hpp

@@ -99,8 +99,8 @@ public:
     wxBoxSizer *      sizer_text_release_note{nullptr};
     Label *           m_staticText_release_note{nullptr};
     wxStaticBitmap*   m_bitmap_open_in_browser;
-    wxHyperlinkCtrl*  m_link_open_in_browser;
     Button*           m_button_skip_version;
+    CheckBox*         m_cb_stable_only;
     Button*           m_button_download;
     Button*           m_button_cancel;
     std::string       url_line;