Allow adding, removing and replacing of published repository components

[cfiehe]

Fixes: https://github.com/aptly-dev/aptly/issues/1338, https://github.com/aptly-dev/aptly/issues/1349, https://github.com/aptly-dev/aptly/issues/1355

Description of the Change

This commit allows to add, remove and update components of published repositories without the need to recreate them.

Checklist

• [x] unit-test added (if change is algorithm)
• [x] functional test added/updated (if change is functional)
• [x] man page updated (if applicable)
• [ ] bash completion updated (if applicable)
• [x] documentation updated
• [x] author name in AUTHORS