Add a list of plugins to always disable on sync

[edjeavons]

Consider if this is the right thing to do vs. listing them in Satellite config every time.

E.g. Wordfence, Sure Feedback

[brettsmason]

I have mixed feels about this.

On the one hand I can see the reasoning, but we support such a mixed bag of new and old sites, the potential list of plugins might be quite big/full of one-offs. And it might lack the flexibility this has at the moment. Definately dont have fixed opinions on this though.