ui: diverse improvements before release

* hide build file content
* use small buttons in all windows
* new design for start screen
* fixed design for enter license ui
* added spacing to summary
* brighter icons in wizzard
* added template icon for graph
* smoothing for graph icons
* switched error icon to dot
* fixed error message tooltip immediatly disappearing
* menu item for opening documentation

src/lib_gui/qt/window/QtMainWindow.h

@@ -98,6 +98,7 @@ public slots:
 
 	QtSettingsWindow* about();
 	void openSettings();
+	void showDocumentation();
 	QtSettingsWindow* showLicenses();
 	QtSettingsWindow* enterLicense();