Refactor InstantSend to use block count instead of local time

68ff166 Fix bug in bitcoin#895

* [devtools] script support for managing source file copyright headers

This is a port of Core bitcoin#8674

Three subcommands to this script:

1) ./copyright_header.py report

Examines git-tracked files with extensions that match:

INCLUDE = ['*.h', '*.cpp', '*.cc', '*.c', '*.py']

Helps to:

-> Identify source files without copyright
-> Identify source files added with something other than "The Bitcoin Core
developers" holder so we can be sure it is appropriate
-> Identify unintentional typos in the copyright line

2) ./copyright_header.py update

Replaces fix-copyright-headers.py. It does file editing in native python
rather than subprocessing out to perl as was the case with
fix-copyright-headers.py. It also shares code with the 'report' functions.

3) ./copyright_header.py insert

Inserts a copyright header into a source file with the proper format and
dates.

* [scripts] Add missing univalue file to copyright_header.py

* Adapt copyright_header.py to the BU repo

- add a new set of expected copyright holders
- define "The Bitcoin Unlimited developers" as the default copyright
holder

c424f0f Fix margins (Alko89)
2d05215 Hide zpiv related options. (Alko89)

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