adding config flags to control all items mentioned in PRIVACY.md

closes #3241
- in config.js, the `privacy` attribute holds all privacy-related flags
- `privacy.tinfoil: true` disables everything (equivalent to setting all flags to false)
- added helper function to core/server/config/index.js to checking privacy flags
- added helper function to core/server/config/index.js to show warning about deprecated items


Once this is merged in, http://support.ghost.org/config needs to be updated with the new config options as well as a link placed in `PRIVACY.md` to indicate how things can be disabled. Below is a sample writeup of how to use the new privacy flags (a potential for the documentation site?)


> Flags to better privacy controls and usage of 3rd party services - see https://github.com/TryGhost/Ghost/blob/master/PRIVACY.md for more details.
> Setting an individual item to `true` indicates that it should not be utilized.
> Settings `privacy.tinfoil` to `true` will ignore all other flags and enable ALL privacy options (same as setting each on to true).
```
privacy: {
    tinfoil: true,
    noUpdateCheck: true,
    noGoogleFonts: true,
    noGravatar: true,
    noRpcPing: true
}
```
How about "useGravatar: true or false" and "useTinfoil: true or false" ?

That way setting something to false consistently disables it and true
enables it (regardless of what "it" is).

It would also still leave the door open more granular stuff (like Hannah's
example of updates)

------
Maurice W.

Sent from a mobile device. Please forgive any typos.
On Sep 7, 2014 3:09 PM, "Fabian Becker" <notifications@github.com> wrote:

> In core/server/controllers/admin.js:
>
> > @@ -12,7 +13,9 @@ adminControllers = {
> >          /*jslint unparam:true*/
> >
> >          function renderIndex() {
> > -            res.render('default');
> > +            res.render('default', {
> > +                skip_google_fonts: config.isPrivacyDisabled('noGoogleFonts')
>
> Absolutely agree.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/TryGhost/Ghost/pull/3874/files#r17216472>.
>