Improve buttons to navigate between modeler and designer

NXS-4115 introduced buttons to quickly navigate between configuration of layouts and data modelling.

However the buttons require some improvements:

• In Modeler, the button should say "Configure layouts in designer" instead of "customize layouts in designer"
• In Designer, the button should say "Configure [page provider/document type/workflow] in modeler".

Style and postion
Bellow the toolbar, like we have in Modeller currently. With same style.