Update Trac design with new style to match O2

[samuelsidler]

We're changing the design of make sites a bit when upgrading them to O2. We should do the same to the related trac instances (meta, core, themes, possibly plugins).

[samuelsidler]

Related: #499.

[ocean90]

@samuelsidler Are there any mockups for this?

[samuelsidler]

Sadly, no. I'll see if I can throw something together.

[Travel_girl]

What kind of mockups (for which sites and views) do you need? Which elements should get redesigned? Do you have a direction where the design should go to?

[obenland]

In 6438:

Trac: Add uparrow for non-plugin Tracs

See #1821.

[obenland]

In 6439:

Trac: Update Trac header styling

Reflects the design changes there that were made on make.wordpress.org.

Fixes #1821.

[obenland]

In 6442:

Trac: Update wporg-footer

Swaps footer link and restores Code is Poetry image.

Props ocean90.
See #1821.

[ocean90]

In 6449:

Trac: Remove bottom border from headline.

See #1821.

[SergeyBiryukov]

In 6540:

Trac: Adjust header styling for Security Trac after [6439].

See #1821.

[SergeyBiryukov]

In 6959:

Trac: Adjust header styling for Build Trac after [6439].

See #1821.