In order to keep plugin class minimal, we propose to put the plugin metadata in a piwik.plugin.json file.
The file is required for third party plugins. The file will be tested on the Plugin Marketplace #4053 when a new release is published (checked against schema / sanity checks)
The file is not required for Core Plugins (bundled with Piwik) since the only attribute that changes between all plugins is the description. The description is automatically loaded by reading the translation key $name_PluginDescription eg. "DBStats_PluginDescription" for the plugin DBStats.
In f4b9656: Refs #4054
* Removing PluginDescription from core en.php files, for all Example* plugins (to showcase the JSON file in the Example plugin)