Add support for an integrated plugin library

Fixes #1450

Provides support for an integrated plugin library that can be used to
install plugins from tiddlywiki.com directly to wikis hosted online or
offline. See the Plugins tab of Control Panel.

Todo:

* Error checking(eg libraryserver.js HTTP GET)
* Translatability
* Documentation
** $:/tags/ServerConnection
** savelibrarytiddlers command

core/ui/ControlPanel/AddPlugins.tid

@@ -0,0 +1,85 @@
+title: $:/core/ui/ControlPanel/Plugins/Add
+tags: $:/tags/ControlPanel/Plugins
+caption: {{$:/language/ControlPanel/Plugins/Add/Caption}}
+
+\define lingo-base() $:/language/ControlPanel/Plugins/
+
+\define install-plugin-button()
+<$button>
+<$action-sendmessage $message="tm-load-plugin-from-library" url={{!!url}} title={{$(assetInfo)$!!original-title}}/>
+<$list filter="[<assetInfo>get[original-title]get[version]]" variable="installedVersion" emptyMessage="""install""">
+reinstall
+</$list>
+</$button>
+\end
+
+\define display-plugin-info()
+<tr>
+<td>
+<<install-plugin-button>>
+<br>
+</td>
+<td>
+''<$view tiddler=<<assetInfo>> field="description"/>''
+<br>
+<$view tiddler=<<assetInfo>> field="original-title"/>
+</td>
+<td>
+<$view tiddler=<<assetInfo>> field="version"/>
+<$list filter="[<assetInfo>get[original-title]get[version]]" variable="installedVersion">
+<br>
+<em>
+Installed:
+<br>
+<$text text=<<installedVersion>>/>
+</em>
+</$list>
+</td>
+</tr>
+\end
+
+\define load-plugin-library-button()
+<$button>
+<$action-sendmessage $message="tm-load-plugin-library" url={{!!url}} infoTitlePrefix="$:/temp/RemoteAssetInfo/"/>
+open plugin library
+</$button>
+\end
+
+\define display-server-connection()
+<$list filter="[all[tiddlers+shadows]tag[$:/tags/ServerConnection]suffix{!!url}]" variable="connectionTiddler" emptyMessage=<<load-plugin-library-button>>>
+
+Search: <$edit-text tiddler="""$:/temp/RemoteAssetSearch/$(currentTiddler)$""" default="" type="search" tag="input" focus="true"/>
+<$select tiddler="$:/temp/RemoteAssetCategory/$(currentTiddler)$" default="plugin">
+<option value="plugin">Plugins</option>
+<option value="theme">Themes</option>
+<option value="language">Languages</option>
+</$select>
+
+<$set name="pluginType" filter="[[$:/temp/RemoteAssetCategory/$(currentTiddler)$]is[tiddler]]" value={{$:/temp/RemoteAssetCategory/$(currentTiddler)$}} emptyValue="plugin">
+<table class="tc-plugin-library-listing">
+<tbody>
+<$list filter="[all[tiddlers+shadows]tag[$:/tags/RemoteAssetInfo]server-url{!!url}original-plugin-type<pluginType>search{$:/temp/RemoteAssetSearch/$(currentTiddler)$}sort[description]]" variable="assetInfo">
+<<display-plugin-info>>
+</$list>
+</tbody>
+</table>
+</$set>
+</$list>
+\end
+
+\define plugin-library-listing()
+<$list filter="[all[tiddlers+shadows]tag[$:/tags/PluginLibrary]]">
+<div class="tc-plugin-library">
+
+!! <$transclude field="caption"><$view field="title"/></$transclude>
+
+<$view field="url"/>
+<<display-server-connection>>
+</div>
+</$list>
+\end
+
+<div>
+<<plugin-library-listing>>
+</div>
+