use go.rice to embed static resources
drop the silly rst2html template needed for html rendering
we don't need DataDir anymore
add go-rice to Makefile dependencies
update documentation
simplify stupid code
remove old code leftovers
fix cancel button in edit page
session cookies must have a path value "/"

If left to the default (empty) value, the cookie path will be set to the
current path component of a URL; this is a problem because subpages will
issue cookies containing the page path as the cookie path.
clean page code