Update 2.x docs for master to manager rename.

[brianloss]

• Update server-properties.md with updated (renamed) properties.
• Update references to master under _docs-2 to manager (not including
  apidocs).
• Document binary/wire incompatibility between 2.0.x and 2.1.
• Update 2.1 release notes with specifics about master/manager renaming.

[ctubbsii]

For the most part, looks good to me. However, we won't be able to merge this and update the 2.x docs until after 2.1 is released.

[brianloss]

For the most part, looks good to me. However, we won't be able to merge this and update the 2.x docs until after 2.1 is released.

@ctubbsii sure, I just wanted to have the docs done. Do you think I should mark this PR as a draft, then? Or do we have some better way to leave it standing until the 2.1 release?

[ctubbsii]

Do you think I should mark this PR as a draft, then? Or do we have some better way to leave it standing until the 2.1 release?

I think the best practice is to just leave it sit for now. We can revisit when we update the site for the 2.1 release. I think there may be another PR in that status as well. It doesn't need to be Draft or anything like that.

[ctubbsii]

@brianloss I created a new base branch to prep changes for the next release, so we can get them merged, and keep them rebased onto main. This one, and #232 are both in that situation at the moment. The changes you made to the Draft release notes, however, can be separated from the rest of the changes in this PR, and merged in to the main branch now. It's just the 2.x docs that can't be merged yet, so should be merged into the next-release branch instead.

[ctubbsii]

I merged this and #232 into the next-release branch, extracted the pieces that could be added to the main branch now in commit b7ce444, and rebased the next-release branch onto that up-to-date main, and created a new PR to eventually merge that branch into main in #265

[brianloss]

I merged this and #232 into the next-release branch, extracted the pieces that could be added to the main branch now in commit b7ce444, and rebased the next-release branch onto that up-to-date main, and created a new PR to eventually merge that branch into main in #265

Thanks for taking care of this!