pmt_io: adding string conversion for uniform vectors

Sadly, this needed expansion of unv_template, otherwise I'd have to
hand-write gengen-style code in pmt_io.cc
volk: adding a binary slicer kernel
volk: adding the generic branchless binary slicer
grc: Fixed scroll functionality in GRC.
Also added clear and scrollback capability for the logging window
grc: Changed dialog to directly call the SCROLL_LOCK and CLEAR_REPORTS actions.
Moved clear reports under view and grouped all Report menu items together
grc: minor edits. removed extra whitespace
grc: fix pad port keys in connect()
grc: remove stray comment in generated flow graph
Merge branch 'maint'
Merge remote-tracking branch 'mmueller/pmt_io_uniform_vector_to_string'

Conflicts:
	gnuradio-runtime/lib/pmt/pmt_int.h
runtime: accessor for message port map & printing more informative error when a msg port is not found
blocks: added I/Q swap option to interleaved_short_to_complex
pager: Add sync code for FLEX 3200 bps 2-FSK encoding
Merge remote-tracking branch 'gnuradio-wg-grc/grc_scroll_fix'
Merge remote-tracking branch 'deuxpi/pager-flex-3200-fsk2'
Merge remote-tracking branch 'nwest/volk_slicer'
uhd: unexposed usrp_sink::get_device() and usrp_source::get_device() from SWIG

* multi_usrp class is not exposed to SWIG, so function returned a SwigPyObject and caused a memory leak when Python exits
* It is not practical to expose multi_usrp to SWIG, so simply tell SWIG to ignore it
volk: cmake: Rename GrBoost to VolkBoost to differentiate it from GR's GrBoost. Although they set the same BOOST variables internally, this change make it clear which cmake file to include.
cmake: Include GrBoost at the top level such that the correct default BOOST variables are set throughout the build. Because of the way CMake handles non-cached variables, each GR component (e.g., Volk) can change the BOOST variables for its particular needs without overriding these default values for other components.
digital: expose set_constellation message port in GRC for constellation_receiver.

Also cleans up white spaces.