Web page front-end for grokdump.

This is a prototype to start discussion about useful features for
a better/friendlier minidump analysis tool.

The change adds an -w option to grokdump.py. With the option on,
grokdump will launch a web server and web browser for browsing the
minidump. It also supports adding persistent comments and listing +
browsing other minidumps (in the same directory) without the need to
restart the web server.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/194573005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20281 ce2b1a6d-e550-0410-aec6-3dcde31c8c00