Continued with project:

Continued with project:
- added showing product's category in admin area
- added method getPrintableProduktCategory() for this
- fixed logger XML file
- added method getCategory() of given Product instance to category database frontend
- added method isProductTitleUsed() to pre-check if the title has been used. This avoids an exception thrown in doAdminAddProduct() which expects that the product's title is not yet used.
Signed-off-by:Roland Häder <roland@mxchange.org>