Add group headings to type dropdown

We’re also reverting to the old custom dropdown. Using the select
widget didn’t work out because it couldn’t cleanly work with a text box
allowing custom types to be specified.
Style updates missed off the last commit
Another select widget demo
Docs updates on Reporting Bugs
Introduce savetiddlers command

Allows us to save tiddlers in their raw format.
Allow the text widget to refresh if needed
Add demo PDF image

That cat again
Typo in 305617b632fd6ecf25cd4be85f4dfb5a5a65dfef

Tsk
Docs update
Introduce setfield command

This new command will let us do the manipulations needed to set up
external image tiddlers