Handle non-image attachments in new media modal

[koopersmith]

Currently the new media modal assumes all attachments are images. Since not all attachments are images, this is probably not a good thing to do.

We should create a way for developers to seamlessly deal with non-image attachments.

Also, if any bugs along these lines crop up, please note them here.

In [21784]:

Use icons for non-image attachments in the new media modal. see #21836, #21390, #21808.

Leaving this ticket open until we have something to handle non-image attachments at the API level.

In [22159]:

Show filenames for non-image attachments in the new media modal.

Also passes all attachment model attributes to the attachment view template by default (instead of selecting specific values).

see #21390, #21836.

In [22170]:

Correctly insert non-image attachments as links.

• Adds wp.media.string.link( attachment ) for printing attachment links.
• Adds the link attribute to Attachment models that corresponds to the link to the attachment post.

see #21390, #21836.

In 22671:

Media: Only show the alignment setting when viewing an image. fixes #21836, see #21390.