[logdog] Add HTML mode to the viewer
[logdog] Add HTML mode to the viewer

This CL implements:
* Rendering HTML when viewing logs (Based on URL query or User agent)
* Full set of user options are now passed to everyone in logData
* Adding favicon and footer logo

Change-Id: I015618203668588f0d07f29d30b7b77a183744be
Reviewed-on: https://chromium-review.googlesource.com/1118760
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Commit-Queue: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go