Fixed #21546 -- Strengthened kqueue detection.

Thanks Loic Bistuer.
Fixed 21406 -- Made blocktrans 'trimmed' option preserve line numbers.

Thanks Bouke Haarsma for report, fix and initial patch.
Added link to localized formatting doc from main index.
Migrate prompts if you need makemigrations, runserver prompts for migrate
Add --dry-run option to makemigrations
Add clone() method to Field to get clean copies of it.
Don't make a second migration if there was a force-null-default addcol.
Fixed #21558 -- Support building CHM files.

Thanks Michał Pasternak.
Migration VCS conflict detection and --merge for makemigrations
List 1.6.x releases in descending order
Merge pull request #2029 from alasdairnicol/releases_ordering

List ed 1.6.x releases in descending order
Fixing manager documentation inaccuracy
Removed 'return' in __init__
Merge pull request #2030 from frankwiles/master

Fixed manager documentation inaccuracy
Fixed a flake8 error
Fix poor variable name (flake8 warning)
Better error reporting when from_app_cache fails
Corrected setting name in gis test error message.
Fixed typo in custom model field documentation.
Fixed another typo in custom model field documentation.