Implement OSCOAP to get security running

[jimsch]

This is not really a request for doing a pull yet, it is more a case of asking for review to see if this is something that you are interested in and if you think that it is in the correct direction.

This is not a complete implementation yet. Some of the things that I know are missing:

• Observe and blockwise transfer are going to require doing a cached exchange in the OSCOAP layer.
• The OSCOAP option number has not been assigned so I have chosen something arbitrary (and wrong) for testing purposes.
• Need to figure out all of the builds to make sure that all of them will build correctly. Part of this is going to be the question of how do do builds for both with and without OSCOAP in all probability given the set of components that I am dragging in for cryptography. Also there may be a problem as not all of the modules that I am currently using are signed and thus if this is signed then they cannot be loaded.