Handle the preview according to the file size

Whatever the size of a document, Nuxeo will try to generate a preview and display it with

<nuxeo-document-preview document="[[document]]"></nuxeo-document-preview>

But, as Nuxeo users are uploading bigger and bigger files, it could lead to performance issues and errors. Last example, a user uploaded a 2GB text file. Nuxeo tries to preview it and start a TXT to PDF conversion by using LibreOffice.

As one can imagine, it failed with a timeout for this conversion and nothing was displayed. And the user also plans to use 4GB Word, Excel and Powerpoint files, so the problem is wide.

Nuxeo should have several guards for that:

• probably one on the UI side, not to preview big files
• another one on the Core side, where a preview (anyToPdf or anytoHtml, maybe anyToPng for thumbnail) is not started is the file is too big (limit to be defined)

Note that ideally, the end user expects that the preview would generate the very first page of the preview, and the other pages would be converted in the background ... not sure it is possible to do that with Binary formats like .doc or .xls