Remove NNG libraries from packages

The default build process will no longer include the NNG
libraries (librmr_nng.*) by default.  It is still possible
to enable them with a CMake build flag (-DBUILD_NNG=1).

The NNG specific unit tests have been disabled.

Some SI95 specific unit tests have been enhanced in an effort
to work toward full coverage of the SI95 code.

This change is in a major version bump as the package contents
change. However, there is NOT an API change; all existing
applications will be able to use the new version without any
modification (other than possibly removing references to the
NNG based libraries).

Issue-ID: RIC-337

Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: Ic9854b1ffc1e82c765692a11724d8086d24cceed