Settings (Your Bio, Basic info): change from "two fields" to "feed of posts"

[xekc]

Following #770 we need to re-work data architecture for user profile to display a feed of posts. User is expected to describe various aspects of his life in a strictly "about me" set of posts.

Those posts don't go into any other feeds (but notifications "user x has updated his bio" are possible + this page might have an RSS feed in the future).

As a part of this task you will need to re-write the code accommodate required features. User's bio basically becomes a small independent micro-blog.

• Current content of the "bio" field should be migrated into a new data architecture and become the "first post". User should be able to edit/delete this post, as any other.
• Each post must have date/time stamp visible on click on "dot" marker (that opens "Delete" / "Edit" menu).
• First post in each user's Bio feed: registration information.
• Both user picture update and profile background picture update posts are out of scope and will be covered in a separate task. We are doing only basic text posts here.
• One post character limit is 200 symbols.
• Full support for line breaks. Markdown support welcomed, but optional for this task.
• No support for links parsing. We'll do it later with markdown or won't do at all.
• In the future each post to this feed (just as each post to any feed) will have a separate URL and will be accessible independently via this URL.