Several disparate changes needed for vendor catalog improvements

- invoke vendor handler where appropriate, e.g. for parsers
- reverse "polarity" of dropdown chooser setting; rename it
- tweak autocomplete behavior yet again, for dynamic values
- auto-select vendor upon parser selection, when possible

tailbone/templates/forms/deform_buefy.mako

@@ -76,6 +76,8 @@
       template: '#${form.component}-template',
       components: {},
       props: {},
+      watch: {},
+      computed: {},
       methods: {
 
           ## TODO: deprecate / remove the latter option here