Create 'gen-test-report' top-level make target

Add new make target so that executing 'make gen-test-report' will run the implementation-report app with all paths/filenames specified.

For instance, just as we can do:

```
mkdir build
cd build
cmake ..
make
make test
```
it would be nice to also be able to say

```
make gen-test-report
```

without having to do anything more complicated.
