Our datagrids were rendering with extra, unwanted <a> tags for some

columns. Part of this was due to an old change that regressed the

link=False semantics, causing this flag to just result in link_func

being ignored rather than disabling linking. Another part was due to the

usage of <div> within <a>, which isn't legal and caused the browser

to do odd things that easily resulted in duplicate tags. Still another

was the need for rendering custom <a> tags as part of the cell data

when in need of a custom CSS class (which often resulted in extra tags

given the link=False breakage).
Now, link=False is respected. When provided, links will not be

generated for the row's object in the data automatically. Similarly, if

link_func fails, the URL won't fall back to the URL for the row's

object.
The <a> tags no longer contain a <div>. Instead, we just assign

display: block to the <a>. The cell also gained a has-link CSS

class to help with styling, so that there's no impact on custom <a>

tags within the cell.
Columns can now accept a link_css_class attribute, which specifies the

CSS class names (or a function returning them) to apply to the <a>,

reducing the work that a column has to do and reducing the amount of

data that must be cached.
This shouldn't outright break any consumers unless they're using

link=False and still expecting links to show up (which wasn't really

ever the intended behavior). However, they can now take advantage of

link_css_class to reduce the data they must render.

Tested with Review Board, both the current upstream and with a change

that takes advantage of the new link_css_class.