Netman tests don't work if we try to effectively execute the config, so
a new parameter to `checkConfig` is introduced, `dontRun` that allows to
skip this phase.
still need to add most options, but this is enough to be usable
right now! This also sets up the work needed for other completion
frameworks, notably things like nvim-cmp and compe.
Created the plugins/plugin-defs.nix file, which will include
definitions for all plugins not in nixpkgs. This way, we can get
rid of the packer dependency and make the whole thing truly
declarative!
