* Refactored control panel “Plugins” tab to make the elements more
reusable
* Refactored the display of plugin tiddlers to use the same format as
the control panel (as suggested, I think by @danielo515), adding the
shadow tiddler listing as an overridable extension tab
* Added a new tab in the “More” sidebar providing quick access to all
installed plugins
* 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
