update links to reference BIP-77 document

[0xZaddyy]

This PR updates all references to BIP-77 by replacing links to the original pull request with direct links to the now merged BIP-77 document in the BIPs master branch.
No other content changes were made.

closes #731

[zealsham]

ACK

Could you squash your commits for a cleaner history

[0xZaddyy]

Done, Thank you!

[spacebear21]

Thanks @0xZaddyy and @zealsham for the review.

ACK, grep-ed the codebase for pull/1483 and found no other instances. I also noticed a BIP78 link referenced a fork of bitcoin/bips so I fixed that in a separate commit.

[0xZaddyy]

I didn't even notice the error with the bip78
Thank you!

[coveralls]

Pull Request Test Coverage Report for Build 15427839047

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 84.833%

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Totals
Change from base Build 15425471520:	0.0%
Covered Lines:	6617
Relevant Lines:	7800

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💛 - Coveralls