Add button-primary class to "Insert into post" button

[lessbloat]

In one of the ​user tests, the user didn't see the "Insert into post" button, and clicked the "Save Changes" button at the bottom instead (See 15:18 from that user test).

It would be nice, as a temporary fix to add a bit of contrast to the "Insert into post" button by changing the class to button-primary.

Shot of what it looks like after the change.

Can 'Insert' be 'Save and Insert'? A bit of clarity means people won't think they have to save things and then insert.

Here's what "Save and Insert" would look like.

I like the resolution, but it seems odd to me to have potentially a ton of "primary actions" on one page. It may work because it'll only show if the section is expanded, but I'd still prefer another way to highlight the function. Attaching a simple mockup of instead changing the background color to indicate "section toolbar" and provide focus on all possible options. Disregard buttons in the bottom, was playing around (unrelated).

Sidenote: I think at the very least not aligning the insert button with the rest of the settings would actually help make it stand out and create that "sign off" feel.

Will no longer be an issue with new media layout/buttons.