Moving Slogger core code out to a separate repo

[mrjcleaver]

Per #275 (comment) , and because of #379 (comment) I'd like to propose we separate Slogger into it's own repo so that nothing that happens in the plugins can break the build of core. It looks like it would not take so much time to implement.

We could also think of having a 'plugins-available' folder akin to apache's sites-available folder, then something like using symlinks or a list of 'plugins-enabled'

I particularly like plugins to be able to specify their own Gemfile as you don't want to install dependencies of things you are not using.
#275 also has mention of how to move Github issues around.

[ttscoff]

@mrjcleaver I'm still totally into this, but have zero time. If you think it's ready for production, I can grant push rights to you to put the new system in place. Sorry that I've slacked on this change.

[mrjcleaver]

For reference, the next action was per #275