Remove 8tiles

Issue
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afui programmatically includes `af.8tiles.js` plugin if win8 is detected, it assumes that user has the plugin in a `plugins` folder, which is not always true. Also user is not aware of this script included automatically, so they may add again in app via `<script>` tag.

Fix
- 
remove automatic plugin inclusion and let user add it in app using `<script>` tag.