Enhancement: Add show file extension toggle switch in file list settings

We've added a toggle switch to the file list settings to turn off and on displaying file extension.

If this setting is turned off, the file extension won't be shown anymore in:
* The name column displayed in the files list
* The right sidebar
* The rename modal
* The new file modal

https://github.com/owncloud/web/pull/6793
https://github.com/owncloud/web/issues/6730
