Please add support for LimeSurvey version 6

I've just installed this plugin manually into a LimeSurvey v6.5 installation by adding:

<compatibility>
    <version>6</version>
</compatibility>

This makes the plugin work for already existing tokens (I actually upgraded this LS from an older version to 6.5), but the token management does not appear on the webpage. From my browser history I was able to find the potential link: (is this correct?)

https://limesurvey.mydomain.com/index.php/admin/pluginhelper?plugin=AuthRemoteToken&sa=fullpagewrapper&method=actionList

This results in an 500 error code:

500: Internal Server Error - Alias ​​"bootstrap.widgets.TbGridView" is invalid. Make sure it points to an existing PHP file and the file is readable.

Please let me know, if more information is required to solve this problem.