Let users set the block instance title for Views blocks in the Block UI

Problem/Motivation

Note: #1967460: Display the block title and populate the machine name for views blocks tries to provide an actionable first step for this issue.

From #1938062: Convert the recent_comments block to a view . Right now, Views goes out of its way to override the block form and prevent the user from creating a Views block instance title different from the View display title. This results in this UX fail:

It basically prevents the UX improvement of #1875260: Make the block title required and allow it to be hidden from taking effect, regresses from D7 in that you can no longer set a block instance title different from the View title, and confuses users by being different from every other block.

Filing as major because this is considered a blocker for all Views block conversions.

Proposed resolution

Allow users to override the View title on the block configuration form.

Remaining tasks

First, see #1967460: Display the block title and populate the machine name for views blocks .

1. We need to find a happy medium between letting content authors configure their block instances, and communicating to users that Views controls the block title dynamically. @yoroy proposed this interaction to resolve the issue:
   http://dl.dropbox.com/u/538835/block-title-overrides.m4v

2. There is also a concern that site builders will no longer be able to control the titles for these blocks once the block is allowed to override it. In #3 (and related issue #1957346: Add some settings on the block display to allow overrides on the block instance configuration ), @dawehner suggested that we might want to allow Views admins to restrict when these settings can be overridden on a per-block level.

3. Finally, we need to find a way to describe what the view title is for the user, since Views sets it dynamically based on conditions like whether the view has no results or what arguments are supplied to it. #1957214: Title setting in views UI does not indicate when the title might be overridden also is exploring this issue within the Views UI itself.