Additional CSS resets to prevent theme conflicts

[jaredatch]

We need to add some additional resets to a few elements of the forum elements to help with theme compatibility.

Specifically the list items within #bbpress. We need to make sure and there is no background images and set a default padding.

Attaching a screenshot of a site that forum user has that is broken due to their theme's CSS conflicting with bbPress.

[jaredatch]

Uploaded screenshots of a few more CSS tweak/resets I think we can include to better our theme compatibility.

Two are dealing with the new search input. We can provide some basic CSS on those so they are tamed.

Secondly is in the search results, .bbp-reply-header uses an h3 which most themes are going to style wildly different. Especially since this is an h3 within the primary content area. They way it looks on bbPress.org looks good, so maybe we can just set similar styling.

[jaredatch]

Patch tames/resets

• bbPress list items. Specifically to make sure there is no background image or padding.
• bbPress search form display. Also hides the .hidden label similar to on bbPress.org
• h3 used in forum, topic, reply titles. Set base size, reset background, border, padding, and text transform.

Tested against TwentyTen/Eleven/Twelve, Genesis 1.8.2, and a few custom client themes.

The search form input sizing (namely the height) is still an issue sometimes, but I figure we probably want to avoid hard coding any dimensions.

[johnjamesjacoby]

In 5007:

Additional CSS resets to improve theme compatibility for search and list items. Props jaredatch. Fixes #2283.