Replace interviewees by non-profit organizations and bitcoinpresscenter.org

While still useful, I suggest we drop the interviewees list (as suggested before #152) and delegate PR to Bitcoin businesses / non-profit organizations like the Foundation & large scale interviewees listing to bitcoinpresscenter.

Building a process to choose interviewees has been time consuming (#152 #161 #162 #167 etc.) and not much progress have been achieved on that front. Current list is mostly unmaintained and despite effort, is still an unsatisfying status quo that differs from what is was intended to be. Many also prefered bitcoin.org to remain as apolitical as possible or have been concerned by unfair visibility.

Fortunately, the situation is different today. Non-profits and Bitcoin businesses now have better dedicated press resources and strategies and there is now many local non-profit organizations. Bitcoin also have been covered much more often and extensively in the news during last months.

Accordingly, I think we could now finally reasonably fix this issue.

Additionally, a future Bitcoin businesses directory could perhaps be linked here, and/or a developers press mailing list for technical questions only.