Modify test env
Change Plugin ID rule.

Plugin class has the number of plugin instances.
A plugin instance has the number of Nth instance of Plugin.

$plugin = new FooPlugin(); // ID: 1
$plugin = new BarPlugin(); // ID: 2
//Plugin::maxId : 2
Change plugin counting.

Change PluginCounter class to singleton.
PluginRepository class count up by each plugin id
Throw exception when PluginRepository can not load plugin
Change methods for chain and Add public methods.

clean: clean plugin repositories
initialize: clean and set basic|bootstrap plugin repositories
Add tests
Add Bootstrap Utility