[PATCH 0 of 4 V3] Improvement of hgweb file views

[Alexander Plavin]

This is a slightly restructured version, and each patch is self-containted (doesn't depend on subsequent ones).
Also highlighting using :target CSS pseudoclass is used where possible (so these places work even without js),
i.e. everywhere but the file annotate view.

Live example is at http://hg.aplavin.ru.

Some comments to previous email replies:
- The current hgweb version has some incosistencies in paddings between e.g. file view and file diff, I (tried to) use the same everywhere.
- As for small selection artifact, pointed by Nicholas Riley, I have no idea about how to get rid of it (and neither users on stackoverflow do :) ). However, it's very minor and not in all browsers.
- It's probably not possible to remove the dot after line numbers for all browsers, keeping the numbers unselectable. But it doesn't seem like a great problem.