gplugin/gplugin

Rename the perl loader to perl5
develop
2020-08-26, Gary Kramlich
e38f74f1b4d8
Rename the perl loader to perl5

Rename the perl plugin to perl5

Testing Done:
Built, tested, verified the docs, and build the debian and fedora packages.

Reviewed at https://reviews.imfreedom.org/r/93/
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 `-Dperl=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`.
## Python
If you're using homebrew, you need to install `pygobject3`.