* The Excise tool only works with tiddlywiki5 format, so only display it on tiddlers that use the tiddlywiki5 parser.
* The Editor Height tool and stamp tool only make sense with text editors, so only display them when the content type starts with text
There have been long standing problems with the buttons not working in
Firefox, and now a [further
problem](https://groups.google.com/d/msg/tiddlywiki/GlsruQyPOag/BAhnI2mt
BgAJ) has come to light, and been similarly hard to resolve.
On balance, I’ve decided to remove the undo/redo buttons from the
toolbar (the ctrl/cmd-Z shortcut is still operational), thus avoiding
the problems, and saving some space in the core.
