Removed the Checker service, removed checker results storage (both in-memory
and the tiny stub of sqlite-based storage). Added ICheckable, all
check/verify is now done by calling the check() method on filenodes and
dirnodes (immutable files, literal files, mutable files, and directory
instances).
Checker results are returned in a Results instance, with an html() method for
display. Checker results have been temporarily removed from the wui directory
listing until we make some other fixes.
Also fixed client.create_node_from_uri() to create LiteralFileNodes properly,
since they have different checking behavior. Previously we were creating full
FileNodes with LIT uris inside, which were downloadable but not checkable.
when rendering a directory in webish, if the url did not correctly include
a trailing slash '/' then the browser will be redirected to a url which
does. this causes any relative links (e.g. the 'other representations'
which are links to files relative to the current directory) to be correctly
intrpreted as relative to the directory in question by the browser.
uses twisted's addSlash mechanism, which is designed for this purpose :-)
