Adding models for sample rate and center frequency drift
Adding hier block "dynamic channel" model which combines these with AWGN and frequency selective fading
grc: adding ability to manipulate set_max_output_buffer based on block properties (please use caution when using this, realize there are a number of other constraints that will ultimately lead to the chosen buffer size)
channels: new block documentation/grc cleanup, dynamic fading model AWGN ampl bug fix
Merge remote-tracking branch 'osh/master'
channels: fix missing blocks in block tree