[Schnorr API BREAK] Improve Schnorr multisigning API + refactoring #318

1. 
   sipa commented at 4:57 pm on September 24, 2015: contributor

   Instead of asking users to manually generate nonces separately and combine them, there are now specific stage1, stage2 and combine functions which generate 1) signed nonces 2) partial signatures 3) full signatures. This is easier, faster, and more secure (by baking signing of nonces into the API).
2. sipa force-pushed on Sep 24, 2015
3. sipa force-pushed on Sep 24, 2015
4. sipa force-pushed on Sep 24, 2015
5. [Schnorr API change] Schnorr multisigning API overhaul 4bba6b1270
6. Refactor Schnorr code 4ecf14285c
7. sipa force-pushed on Sep 25, 2015
8. Move schnorr documentation to markdown document d889fbba7d
9. sipa force-pushed on Sep 25, 2015
10. 
    sipa commented at 9:49 pm on September 25, 2015: contributor

    Added a document explaining Schnorr single and multisigning.
11. 
    sipa commented at 7:45 pm on September 28, 2015: contributor

    Superseded by #322.
12. sipa closed this on Sep 28, 2015

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