Closes #4290

Closes #4287

Sanitizes HTML comments inside PR body for BitBucket server.
Includes snapshots for the tests.

Closes #3715

`rebaseConflictedPrs` is used to enable or disable auto-rebase
in case of merge conflicts with the master branch. It is `true`
by default which means branches will be rebased if there are conflicts
in a PR. By setting it to `false`, Renovate no longer will rebase it
with the master branch if there are merge conflicts.

Refer #4184

Only changed incorrect use of words and not each and every
grammatical changes.

Refer: #4277