* provides a "close plugin library" button
* starting from #1718 by @inmysocks
* possibly fixes all of #1718, #1597, and #2067
* corrected code comment
* add back title
No idea why I overlooked this beforehand.
Next time I will not suggest such changes that have little to do with
the PR, but rather just comment the code.
* ah, sorry, "fixed" wrong spot
now
```
<$action-sendmessage $message="tm-load-plugin-from-library"
url={{!!url}} title={{$(assetInfo)$!!original-title}}/>
```
...should be back at the right spot.
* mhhh... still fixing the mess
load, unload, puh... let's see if I got it now
* added unloadIFrame and minor syntax fixes
* Moved “add new plugin” into a modal wizard
* Adopt big friendly buttons
* Add plugin icons and readmes to “add new plugin” modal
* Use tabs for splitting plugins/themes/languages
* Consistent styling between the “add new plugin” modal and the
“installed plugins” control panel tab
* Behind the scenes, moved from addressing the library as
`recipes/defaults/tiddlers/<etc>` to `recipes/library/tiddlers<etc>`
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
