YML API fixes and timeout messaging fixes

[tfcollins]

PR fixes specifically for 3.8+ new yml block callbacks and fixes #70

[commodo]

commits could use some descriptions;

also curios: how much effort would it be to update the build to pass?

-- Build type not specified: defaulting to release.

CMake Error at CMakeLists.txt:86 (find_package):

  Could not find a configuration file for package "Gnuradio" that is

  compatible with requested version "3.8".

  The following configuration files were considered but not accepted:

    /usr/local/lib/cmake/gnuradio/GnuradioConfig.cmake, version: 3.7.12.0

[commodo]

otherwise, rest looks good

[tfcollins]

Would need to upgrade gnuradio to 3.8 which is a big change (at least on windows).