Make ndn-lite library compatible with more models of nRF board besides nRF52840

[peurpdapeurp]

As was discovered by Paul-HIT in issue #23, the current ndn-lite library adaptation to the nordic sdk only works on the nRF2840, and not other boards like the nRF52 DK.

Code needs to be added in order to make sure that the ndn-lite library adaptation (particularly with regards to BLE functionality) is compatible with all or at least most variations of the Nordic boards.

[peurpdapeurp]

I discussed this issue with my labmates and professor, and they suggested that we ask the person who was struggling to get our library to work on the pca10040 board to possibly assist us in making the ndn-lite adaptation code work for that board.

I think that the difference should only be in the files that are included, but any help in pinpointing exactly what the issue of getting our code to work with the pca 10040 board is would be greatly appreciated.