GitLab

Now the user doesn't have to supply a visitor capable of visiting all
layers, but instead just the ones they are interested in.  Also added
visit_computational_layers() and visit_computational_layers_range()
since those capture a very common use case more concisely than
visit_layers().  That is, users generally want to mess with the
computational layers specifically as those are the stateful layers.

* fix some warnings when running tests

* rever changes in CMakeLists.txt

* update example make use of newly promoted method

* update tests to make use of newly promoted methods

* simplify definition by reusing struct template parameter

* put resnet into its own namespace

* fix infer names

* rename struct impl to def

* Add dnn_introduction3_ex