introduce sample selection list (model & view) - the left pane of the new layer oriented sample editor

Get rid of message "DEBUG: bool QCPLayoutGrid::addElement(int, int, QCPLayoutElement*) There is already an element in the specified row/column: 0 1"

move item infos to item catalog (in the future the info will be used at different locations, not only the sample toolbox)

move example infos to example factory (in the future the info will be used at different locations, not only the sample toolbox)

... to have a std::bad_function_call exception in case of an uninitialized function pointer