Stop generating static content when we're saving an encrypted wiki
Add [is[tiddler]] filter operator

For selecting all non-shadow tiddlers, whether or not they are system
tiddlers
Rejig the main save template to get rid of the separate system tiddler area

It dates from an ancient version of TW5, and is really redundant now.
It also meant that system tiddlers were not encrypted, which seems
confusing for end users.