ITE and Specification updates to note

[Aditya Sirish A Yelgundhalli]

Hello everyone, following up from the community meeting on Friday, here
are some changes we are considering.

First, we're proposing a minor tweak to the ITE process where
modifications to accepted and beyond ITEs must be accompanied with a
changelog. https://github.com/in-toto/ITE/pull/36 adds this to ITE-1.
This was motivated by https://github.com/in-toto/ITE/pull/35 where we
moved the specification of the old signature wrapper out of the in-toto
spec to an appendix in (accepted) ITE-5. Also, even though #35, please
reach out if you believe we should go a different route with preserving
the specification of the old wrapper.

Second, we're preparing to tag v1.0 of the specification and we want to
address minor inconsistencies and such before we do so. I took a pass at
it (https://github.com/in-toto/docs/pull/69), please feel free to point
out anything else you think should be addressed pre-v1.0.

Thanks,
Aditya