DarkConsole: fix rendering, move request log, load over ajax

Summary:
This accomplishes three major goals:

1. Fixes phutil_render_tag -> phutil_tag callsites in DarkConsole.
2. Moves the Ajax request log to a new panel on the left. This panel (and the tabs panel) get scrollbars when they get large, instead of making the page constantly scroll down.
3. Loads the panel content over ajax, instead of dumping it into the page body / ajax response body. I've been planning to do this for about 3 years, which is why the plugins are architected the way they are. This should make debugging easier by making response bodies not be 50%+ darkconsole stuff.

Additionally, load the plugins dynamically (the old method predates library maps and PhutilSymbolLoader).

Test Plan:
{F30675}

• Switched between requests and tabs, reloaded page, saw same tab.
• Used "analyze queries", "profile page", triggered errors.
• Verified page does not load anything by default if dark console is closed with Charles.
• Generally banged on it a bit.

Reviewers: vrana, btrahan, chad

Reviewed By: vrana

CC: aran

Maniphest Tasks: T2432

Differential Revision: https://secure.phabricator.com/D4692