Get media modal to play nice with P2 theme

[lessbloat]

There are a few places where we can improve styles for the front-end media modal in the P2 theme.

Note that some of this may simply be P2's problem. But, if there's anything we're doing that is fairly silly or lame, we should fix it. A few reset rules didn't hurt anyone.

22752.diff​ cleans up a few things:

• Removes a:hover border bottom
• Adjust layout of .link-to-custom field
• Adds some margin to the bottom of .post-upload-ui
• Fixes alignment for selected images (.selection-view)

The only thing that stood out to me that should get fixed in the theme is the add media button:

in 22752.2.diff:

• I removed border-bottom: none; for a:hover (Helenyhou brought down her fist ;-) - this will need to be done in the P2 theme)
• Removed the .link-to-custom style as it displays differently cross-browser
• Changed the magic number (23px) to something a little less magic (2em)

Just so I don't sound crazy, I brought down my fist because there is a line where we can't account for things, and it's best not to cross it. Where would it stop? All borders? Strikethrough? Background? Etc.

In any case, 22752.2.diff​ looks good to me. Doesn't seem to have adverse effects within the admin, either.

Let's bring back border-bottom: none, per IRC. Otherwise, .2.diff.

Also, the select elements are squished. Maybe we should also normalize those the way we do in the admin? (Do we?)

22752.3.diff:

• Adds border-bottom: none back in
• Attempts to fix select box formatting

Tightens up .link-to-custom (thanks Helenyhou)

22741.4.patch​ looks good to me.

2px padding for .media-frame select (instead of 3px)

Caught that select padding is actually 2px for the admin at large. .5 contains that little change.

I'm +1 on this. Leaving it for Nacin to commit when he wakes up since he had some opinions on it.

In 23077:

Media: Account for the most obvious and common style conflicts that may occur when the media modal is loaded on the frontend. Tested primarily with P2. props lessbloat, helenyhou. fixes #22752.

I moved border-bottom: none to .media-frame a, because that will handle overriding a :hover style (as it is a, not a:link).