Add "cascade" filter run prefix and use it to control view templates (#6168)

* Initial Commit

* Set currentTiddler and ..currentTiddler for filter evaulation

* Precompile the filters for performance

* Add explicit test for empty result when no filter passes

* Use the cascade filter run prefix to choose the view template body template

* Use the cascade mechanism to choose between the edit and view templates

* Simplify cascade filter

Thanks @saqimtiaz

* Add control panel UI for inspecting the template cascades

* Refactor import listing and plugin listing as alternate body templates

As suggested by @pmario

* Refer to $:/core/ui/{View|Edit}Template via their associated config tiddlers

* Fix typo in previous commit

* Add demo of custom story tiddler template

* Tweak control panel wording

* Standardise "Story Tiddler Template" nomenclature

* Add a cascade for the editor template body

* Add a cascade for the view template title

* Avoid unwanted whitespace

* Add a cascade for dynamically choosing tiddler icons

core/ui/ControlPanel/Cascades/EditTemplateBody.tid

@@ -0,0 +1,9 @@
+title: $:/core/ui/ControlPanel/EditTemplateBody
+tags: $:/tags/ControlPanel/Cascade
+caption: {{$:/language/ControlPanel/EditTemplateBody/Caption}}
+
+\define lingo-base() $:/language/ControlPanel/EditTemplateBody/
+
+<<lingo Hint>>
+
+{{$:/tags/EditTemplateBodyFilter||$:/snippets/ListTaggedCascade}}

core/ui/ControlPanel/Cascades/StoryTiddler.tid

@@ -0,0 +1,9 @@
+title: $:/core/ui/ControlPanel/StoryTiddler
+tags: $:/tags/ControlPanel/Cascades
+caption: {{$:/language/ControlPanel/StoryTiddler/Caption}}
+
+\define lingo-base() $:/language/ControlPanel/StoryTiddler/
+
+<<lingo Hint>>
+
+{{$:/tags/StoryTiddlerTemplateFilter||$:/snippets/ListTaggedCascade}}

core/ui/ControlPanel/Cascades/TiddlerIcon.tid

@@ -0,0 +1,9 @@
+title: $:/core/ui/ControlPanel/TiddlerIcon
+tags: $:/tags/ControlPanel/Cascades
+caption: {{$:/language/ControlPanel/TiddlerIcon/Caption}}
+
+\define lingo-base() $:/language/ControlPanel/TiddlerIcon/
+
+<<lingo Hint>>
+
+{{$:/tags/TiddlerIconFilter||$:/snippets/ListTaggedCascade}}

core/ui/ControlPanel/Cascades/ViewTemplateBody.tid

@@ -0,0 +1,9 @@
+title: $:/core/ui/ControlPanel/ViewTemplateBody
+tags: $:/tags/ControlPanel/Cascades
+caption: {{$:/language/ControlPanel/ViewTemplateBody/Caption}}
+
+\define lingo-base() $:/language/ControlPanel/ViewTemplateBody/
+
+<<lingo Hint>>
+
+{{$:/tags/ViewTemplateBodyFilter||$:/snippets/ListTaggedCascade}}

core/ui/ControlPanel/Cascades/ViewTemplateTitle.tid

@@ -0,0 +1,9 @@
+title: $:/core/ui/ControlPanel/ViewTemplateTitle
+tags: $:/tags/ControlPanel/Cascades
+caption: {{$:/language/ControlPanel/ViewTemplateTitle/Caption}}
+
+\define lingo-base() $:/language/ControlPanel/ViewTemplateTitle/
+
+<<lingo Hint>>
+
+{{$:/tags/ViewTemplateTitleFilter||$:/snippets/ListTaggedCascade}}