Adds two properties to `Status` entity:
* `reblog` - contains the reblogged Status or None if not a reblog
* `original`- contains the reblogged Status or self if not a reblog
Anywhere where you wish to show a reblogged status's property when it's
a reblog, or the base status proprety if not a reblog, use
`status.original.<property>`.
We add a "mentions" attribute to Status. Then when composing a reply, we
fill the edit text of the compose box with the account name of status
being replied to and possibly include mentions at the bottom of the edit
text. Initial cursor position is set after replied account name.
This is different from the "reblogged" yellow icon already displayed on
the left of account name which indicates if own status got reblogged.
This one indicates if displayed status is a reblog.
When the status is a reblog, the URL of the original toot should be used
as the one of reblog is null.
We add a "url" attribute to Status class storing computed URL.
