Add alt attribute to image widget
Refactor saver handler

Fixing problems caused by c4b76ceb0bc786bcceb12fc3417bb8c4bfde27a9:

* We still need to initialise the saver-handler even when syncing to a
server, otherwise offline snapshots can’t be saved
* We need to override the default save template a bit further up the
stack, to avoid the server side serving the offline version of the wiki
at `/`
Add content to "Contents" tiddler

Leaving it with no text content means that it triggers a lazy load with
the client server edition
Use a JSON tiddler for $:/config/OriginalTiddlerPaths

Otherwise things go wrong when we have tiddler titles containing colons
Add star image
Add banner soliciting documentation improvements

A first pass