New System Explorer tab in sidebar (#2881)

* Create System-Explorer.tid

* Fixes problem with syslink parser

core/ui/MoreSideBar/System-Explorer.tid

@@ -0,0 +1,60 @@
+title: $:/core/ui/MoreSideBar/System-Explorer
+tags: $:/tags/MoreSideBar
+caption: {{$:/language/SideBar/System-Explorer/Caption}}
+
+\define cleanChunk()
+<$list filter="[[$(chunk)$]] +[removesuffix[/]]" variable="cleanChunk">
+<$text text=<<cleanChunk>>/>
+</$list>
+\end
+
+\define leafnode(prefix)
+<li>
+<$list filter="""[[$prefix$$(chunk)$]is[shadow]] [[$prefix$$(chunk)$]is[tiddler]] +[removeprefix[$prefix$]] +[limit[1]]""" 
+emptyMessage="""<$text text="$prefix$$(chunk)$"/>""">
+<button class="tc-btn-invisible" disabled>{{$:/core/images/blank}}</button> <$link to="""$prefix$$(chunk)$""">
+<$view field="title"/>
+</$link> 
+</$list>
+</li>
+\end
+
+\define branchnode(prefix)
+<$reveal type="nomatch" text="" default="""$(chunk)$""">
+<li>       
+<$list filter="""[all[shadows+tiddlers]prefix[$prefix$$(chunk)$]] -[[$prefix$$(chunk)$]] +[limit[1]]""">
+<$reveal type="nomatch" state="""$:/state/tree/$prefix$$(chunk)$""" text="show">
+<$button set="""$:/state/tree/$prefix$$(chunk)$""" setTo="show" class="tc-btn-invisible">{{$:/core/images/right-arrow}}</$button>
+</$reveal>
+<$reveal type="match" state="""$:/state/tree/$prefix$$(chunk)$""" text="show">
+<$button set="""$:/state/tree/$prefix$$(chunk)$""" setTo="hide" class="tc-btn-invisible">{{$:/core/images/down-arrow}}</$button>
+</$reveal>
+</$list>
+
+<<cleanChunk>>
+
+<$list filter="""[all[shadows+tiddlers]prefix[$prefix$$(chunk)$]] -[[$prefix$$(chunk)$]] +[limit[1]]""">(<$count filter="""[all[shadows+tiddlers]prefix[$prefix$$(chunk)$]] -[[$prefix$$(chunk)$]]"""/>)
+<$reveal type="match" state="""$:/state/tree/$prefix$$(chunk)$""" text="show">
+<$macrocall $name="tree" prefix="""$prefix$$(chunk)$"""/>
+</$reveal>
+</$list>
+
+</li>
+</$reveal>
+\end
+
+\define tree(prefix)
+<ol>
+<$list filter="[all[shadows+tiddlers]removeprefix[$prefix$]splitbefore[/]sort[title]] +[!suffix[/]]" variable="chunk">
+<<leafnode """$prefix$""">>
+</$list>
+
+<$list filter="[all[shadows+tiddlers]removeprefix[$prefix$]splitbefore[/]sort[title]] +[suffix[/]]" variable="chunk">
+<<branchnode """$prefix$""">>
+</$list>
+</ol>
+\end
+
+<div class="tc-table-of-contents">
+<<tree "$:/">>
+</div>