gplugin/gplugin

Finally replace bitbucket.org with keep.imfreedom.org

2020-09-21, Gary Kramlich
2116940747cd
Finally replace bitbucket.org with keep.imfreedom.org

Testing Done:
compiled and ran gplugin-gtk-viewer.

Reviewed at https://reviews.imfreedom.org/r/129/
There are a few notes about building on OSX.
First off, building has *ONLY* been tested against homebrew. If you want to
support fink or macports, please let me know and I will merge your pull
request.
Currently there is no known way to build the Perl loader on MacOS. So you
**MUST** run meson with `-Dperl5=false`.
## Lua
For the Lua loader to work, you need to install `lgi` from luarocks either
systemwide or to a virtual environment created by LuaDist, vert, or something
along those lines, then you just need to run `luarocks install lgi`.
## Python3
If you're using homebrew, you need to install `pygobject3`.