Include bootstrap assets and it's dependents


As only bootstrap.css was there. So, we have to write html code to include Bootstrap-theme.css and bootstrap.js. This change is important.  And remove all other bootstrap asset files such as BootstrapPluginAsset.php and also BootstrapYhemeAsset.php. 

```php
If user wants to use bootstrap, then they should easily use 1 file instead of using 3 files everywhere.
So, it is important pull request.
```

As bootstrap is dependent on Jquery Library, So, also included jquery dependency in it.