#292 add Statdtbilder method in SingleStadtbildJGrid

When all stadtbilder in the warenkorb are selected, this method can be
used to add the stadtbilder to the warenkorb grid
 #292 selectAll methods with fire events paramter

added a selectAllStadtbilder methods that takes a boolean as the second
parameter. this parameter can be used to fire or surpress the selection
events for a single stadtbild
closed #292

don't fire events when calling selectAllStadtbilder. Save a list of
stadtbilder for that a high resolution is available. when
stadtBildChoosen events are fired, use this list to determine the button
status of the download button
Merge branch 'feature/292-stadtbilder-performance-improvements' into dev