Review all the things (please...)

All,

I have reviewed a little over half of the GitHub issues
<https://github.com/w3c/webcrypto/issues> and either addressed them,
proposed changes or referenced existing proposals.

Please review those open issues marked "needs review", "needs input" or
"wontfix": these are all waiting on working group input of one kind or
another to make progress.

I have erred on the side of speed with these proposals, so I expect review
comments :-)

...Mark