added failing test when image is in footer and document.xml
created ImgReplacer@getImageName which returns the next available
imagePath

 * Created hasImage metho in Imgmanager
 * created imgmanager@getFullPath and using it
using the same mockedqrcode for all errors, and using num instead of @xmlTemplater.DocxGen.qrCodeNumCallBack
regression test: use qrcode in footer and document (solves #103)
added some error cases