Bug#683046: Thumbnailer is not registered automatically

[IRIE Shinsuke]

The thumbnailer should work with the following .thumbnailer file:

================================ START ===============================
[Thumbnailer Entry]
TryExec=/usr/lib/blender/scripts/blender-thumbnailer.py
Exec=/usr/lib/blender/scripts/blender-thumbnailer.py %i %o
MimeType=application/x-blender;
================================ E N D ===============================

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IRIE Shinsuke