Hide 'Sign in' header link on the connection page

Improve adding posts to stream

Call autosize when changing input via markdown editor

Improve responsive header in desktop version

Fixes #7521

Update the user data export archive format.

Fix Person.in_aspects scope to return each person only once when the
person is in multiple aspects.

That should increase test coverage percentage

spec/spec is a new folder for "tests for tests"

This commit introduces changes to the user data export archive format.
This extends data set which is included in the archive. This data can be
then imported to other pods when this feature is implemented.

Also the commit adds the archive format json schema. ATM it is used in
automatic tests only, but in future it will also be used to validate
incoming archives.

Include count in mobile post action link and increase reshare counter after reshare

Prevent publisher from closing in preview mode

Move back to top to the right to avoid misclicks

Update markdown-it

Fixes #7245

Add markdown editor on conversations and comments

Javascript refactorings for better maintainability:
* simplePreview function to avoid code duplication
* Preloaded conversation is processed in a slightly different way
* Split isPreviewOrTexareaNotEmpty function since it has more than one responsibility

This class is capable of quering a list of people from authors of given posts that are non-contacts of a given
user.