docs: Add release notes for v1.7.0.

[davecgh]

This is currently the release notes for rc1 for the purposes of review. It will be updated to remove the RC status and merged once the final non-rc release is ready.

[jzbz]

full administrative priveleges. -> privileges.

[rstaudt2]

Looks great to me. It must have taken quite some time to go through all those PRs.

Since there are so many performance enhancements in this release, I ran some initial sync tests to see the overall relative difference in performance between release-v1.6 and release-v1.7. Based on my testing:

• release-v1.7 is ~47.87% faster than release-v1.6 with default settings
• release-v1.7 is ~39.36% faster than release-v1.6 when using the latest checkpoint from 1.6 (this is to compare without giving release-v1.7 the advantage of a more recent checkpoint)
• release-v1.7 is ~29.37% faster than release-v1.6 with checkpoints disabled

Details of the tests I ran are in this gist.

[dnldd]

Reads well. Only thing I noticed which could be improved is punctuation for list items with sentences, a few are punctuated while majority are not.

[davecgh]

Thanks for those numbers @rstaudt2. I added a section entitled Substantially Reduced Initial Sync Time that uses the first value since that is what most users reading the release notes can expect to observe. It's nice to see the other numbers as well. The difference between checkpoints and no checkpoints shows pretty clearly that UTXOs are what dominates.

I went back and forth a bit on whether to include the others, but I think it's probably better to keep it more high level to strike a balance.

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I also updated the Unspent Transaction Output Cache section to make the bullet points more succinct and consistent with the rest (single sentences, no periods) per @dnldd.

[rstaudt2]

I added a section entitled Substantially Reduced Initial Sync Time that uses the first value since that is what most users reading the release notes can expect to observe.

Nice, that looks good to me. Agreed that the first value makes the most sense to put there.