Some embedded static improvements

I worked the embedded static subsite into notmuch-web, see
https://bitbucket.org/wuzzeb/notmuch-web/commits/fe644b68e2b47b3e3b4c267b8a2ccb3ae3a3830d
the commit is large since I unminimized the javascript, but
https://bitbucket.org/wuzzeb/notmuch-web/src/fe644b68e2b47b3e3b4c267b8a2ccb3ae3a3830d/src/StaticFiles.hs
is the use of the embedded static subsite so you can see an example.  I have done some testing and it seems to work, I will do some more testing though.

As I mentioned several times, I had this javascript license label code which would automatically build a javascript license label table inside the embedded static subsite.  But when trying to work it into notmuch-web it was too complicated. The generic API that was needed in yesod-static was hard to use in the application.  So I decided to dump the label stuff and instead just keep the license comment in the file (the extra bandwidth isn't too bad since it is cached in any case).  To support this I added the keepFirstComment generator in the first commit.

The second commit contains some helper messages since I try several compressor tools in notmuch-web.