Mercurial 4.0 release

/!\ This is a draft and may not accurately reflect what lands in the 4.0 release.

1. Features

* The following commands now also have formatter support: 'hg version', 'hg grep' and 'hg config'

2. Improvements

* A number of changes were made to move and copy tracking, to make sure move and copy information is not lost during commands like 'hg graft' * Python 3 support has received a lot of improvements (but will take a lot of additional work)


3. Raw draft changelog

3.1. commands

3.2. core

3.3. extensions

3.4. hgweb