Change relative path of configure files in CMakeLists.

that contain a different number of samples than their input tensors.

Using CMAKE_PROJECT_DIR instead of CMAKE_SOURCE_DIR/../dlib
makes the build process more portable.

installed on windows via pip.

vector from that layer so that it can be reused in any computations.
Most layers won't use it but for some backward computations having it
allows them to be implemented more efficiently.