Major Milestone in v3.7 Progress

Earlier this week, we finished converting all of the main blocks over to the new 3.7 style and top-level components. We still haven't fully addressed gr-atsc and gr-shd, but I'm holding off on those two right now on purpose.

The main win here is that you will only see minor changes in which modules you pull blocks in from. Any changes now are bug fixes, but they will be minor and easily corrected. So you can now rebuild your Python and GRC flowgraphs around the 'next' branch, and you should be pretty much good to go.

Note that we've removed an 'blocks' from gnuradio-core. So now, the only things you pull in from the Python gr. module are data structure sizes, the top block, message queue stuff, and similar. If it's a block, it's now located in one of the other blocks. We'll try to post our spreadsheet of where each block is now, but hopefully we've done it so it's pretty intuitive. And if you don't know where something should be, it's probable in gr-blocks (from gnuradio import blocks).

We're really starting to close in on the release of 3.7, so the major churn from our users' perspective should be slowing down.