grc: design time values for object-like variables
digital: using new var_value for constellation variables
grc: allow blocks to dynamically hide some of their ports
cmake: adds a NoOptWithASM build type for building with assembly output and no optimizations for better debugging.
blocks: Added multiply_matrix_ff

This block maps inputs to outputs by matrix multiplication.
Also includes QA.
blocks: Added multiply_matrix_cc
uhd: Updated docs, in particular for the command interface
uhd: Added command interface to uhd source, modified command syntax
uhd: Refactored common stuff from usrp sink and source
uhd: Added GRC bindings for command interface
uhd: Added more type checking and flexibility to commands and tags
uhd: Added example for re-tuning through messages
uhd: Added checks for lock sensors.

When operating with an external ref, in MIMO mode or with a GPSDO,
the constructor now waits until the lock sensors report succesful
locking.
If this fails, a warning is displayed using the logger interface,
to keep backward compatibility.
cmake: update revision to 3.7.5git after release
Add async message port to switch muting on and off.
build: missed gnuradio-uhd in static libs build.
Merge remote-tracking branch 'gnuradio-wg-grc/grc_variable_blocks'
Merge remote-tracking branch 'gnuradio-wg-grc/grc_hide_ports'

Conflicts:
	grc/base/Port.py
	grc/gui/Block.py
grc: fixing xml files of some blocks with message control ports to be able to hide/show them as wanted.
grc: fixing some spacing issues in various xml files.