This was frustrating problem to many users for not having base map printed together with data from QGIS project. Solution with this release is pragmatic more of a workaround because QGIS server only generates print map from QGIS project. You add base layer also to QGIS project but Web Client will use it only for printing if such layer name also exists in database and is added to project as external layer. More information
More project configuration options
New configuration options were added to database to control each project. Now you can simply enable/disable buttons below with single database click:
zoom navigation buttons (back, forward)
Search combo now also with local data
Search combo can now be configured to use WSGI search on your Postgis data (one or more tables). In next minor release following shortly this will also work on mobile client.