Prepare API documentation for v 1.0 release

[crandmck]

Update comments used in documentation:

• Change C2PA spec version number as appropriate. Some comments still refer to v 1.0.
• Remove outdated references to v1_api stuff, eg. to ManifestStore. While it's still applicable for apps using v1_api, they are no longer relevant in the new API world.

What else do we need to do for docs to release a real version 1.0?

PR: #1178

Generate docs locally

Use this command:

make doc