Removed the old security system.

Signed-off-by: Wolf480pl <wolf480@interia.pl>
Added CommonPolicy.CommonPermissionCollection

Signed-off-by: Wolf480pl <wolf480@interia.pl>
Added YamlConfiguration to CommonPolicy

Signed-off-by: Wolf480pl <wolf480@interia.pl>
Added BrowserPermission
Added Client.openBrowser(URI)

Signed-off-by: Wolf480pl <wolf480@interia.pl>
Added required and optional clearances to PluginDescriptionFile.
Don't load the plugin at all, if the required clearances are not
granted.
Started adding default plugin permissions.