Fixed adaptToBackend and added unit test

This fix include the following:

• Correct several critical bugs in OperatorImpl::getAdaptation() (which was not working correctly at all: data type and format was inverted and the added nodes were dangling after going out of scope);
• Add unit test for the adaptToBackend() recipe;
• Add diagnostic messages in Node class to detect dangling connections (if a dangling connection is detected, a warning is issued, and in debug with Log Debug level, a message is emitted if a node is added as a child with a ref count of 1, because it may lead to a dangling connection if the child node goes out of scope and is destructed);
• Corrected bug in getDataFormatTranspose(), which was not returning the correct transpose vector if destination format was Default;
• Added assert in Tensor::copyTranspose() to check the validity of input implementation;
• GraphView::save() now displays the node backend if the verbose argument is true.