Tag release 0.5 for Pothos framework + GUI

[guruofquality]

The big checklist

• [x] tag submodules with maint changes
• [x] update maint branch submodules
• [x] tag latest 0.4 on maint branch
• [x] remove -dev suffix on ABI on master
• debian suffix updates, tag, master->maint:
  • [x] audio
  • [x] blocks
  • [x] comms
  • [x] gui
  • [x] plotters
  • [x] python
  • [x] sdr
  • [x] widgets
• [x] update submodules on master
• [x] tag 0.5 on master
• [x] update homebrew tags
• [x] update maint branch to tag
• [x] update gh-pages for 0.4, 0.5 tag + latest

Changelog for summary

• BlockEval API changes to support GUI evaluator
• DocUtils API changes to support GUI docs query
• Removed the pothos-serialization dependency and replaced it with a much smaller in-library solution. The serialization format has changed for this release.
• Switch stdio to end of line flushing for logging
• Added Plugin path API for concatenating two paths
• Added API for parsing sources for block descriptions
• Created configuration-file based loader for plugins:
  • With built-in loader for JSON topologies
  • With built-in loader for JIT compilation
  • With built-in loader for block descriptions
• Added PluginModule boolean operator for checking null
• Reimplemented compiler support around file paths
• Reimplemented QFormat for simplification and warnings

And gui changelog

• Require 0.5.0 Pothos framework for DocUtil and BlockEval
• Switch over to Qt classes for JSON, time, processes, etc...
• Parameter edit mode to switch between default and line entry
• Finer grained connection management in Topology evaluator
• Support for querying and applying block description overlays

[guruofquality]

Release 0.5 is out, and many toolkits updated. Windows installer and PPAs will be updated after SoapySDR has been tagged and releases as well.