Merge branch 'feature/plugin-support'

* feature/plugin-support:
  Plugin interface uses memory pointers, so that plugins can directly manipulate variables being used in the program. 
  Getting closer to a usable plugin interface, there are now variables passed to the plugin "hooks" 
  Docker: Build default plugins along with the main binary, before packing 
  Makefile: Build plugins with `make build-plugins`, don't auto-rebuild everything
  Better public/private-ness of types and variables, better plugin example, first actually-working basic plugin interface. 
  Makefile support for creating non-stripped builds with full debug support.
  Make all types and structs public 
  Robustness and logging in the extension/plugin loader  
  Update Makefile to build from `src` directory 
  Modularise code and move into src subdirectory 
  Ignore `.idea` directory (when using IntelliJ / GoLand or similar) 
  Update plugin example and document plugin configuration 
  Begin work on modularisation, documentation, and plugin support