Add section how to cope with private data

Dear Gerard and Hugues,

I just suggested in the short call with Gerard to add a section to the 
architecture 
documenthttps://w3c.github.io/voiceinteraction/voice%20interaction%20drafts/paArchitecture/paArchitecture-1-3.htm#errorhandling 
how to cope with private data.

I suggest to add this as a new section 3.3.6 as private data is 
potentially sent to

  * External IPA Providers
  * External Services
  * Data Providers

and would relate to them.

The document that we are currently working on is here: 
https://github.com/w3c/voiceinteraction/blob/master/voice%20interaction%20drafts/paArchitecture/paArchitecture-1-3.htm

The same is described in https://github.com/w3c/voiceinteraction/issues/53

Let me know, if you have any questions.

@Debbie

I think Gerard and Hugues should become members of that GitHub 
repository https://github.com/w3c/voiceinteraction to do so. Could you 
help to get access for them?

Dirk