* Updates to make Excision more friendly to Markdown users by adding
Markdown as an option in the criteria to use excision and by making the
excise operation reuse the type of the tiddler being excised.
* Updated excise operation to use Markdown syntax for links.
* 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
