gitignore: *.thumbs.db .gitattributes: *.jpg/*.hdr binary

Windows automatically create a hidden file to handle image's thumbnails.
gitattributes not to diff (bigs) jpg et hdr.
Note: GitHub don't take into account (yet?) gitattributes so it will still show diff but only on the site.
Added more controls and fixes to tonemapping + new template

Added "locality" control to decide which mipmap level to fetch for the avg.
This enable local tonemapping.
Doing this, I discovered that the luminance scaling was actually wrong (denominator/numerator)
The scenes now load correctly on first selection, the mipmap generation was done before the scene had finished loading.
Added brightness, contrast and saturation controls (may contains bugs)
The sample now uses the template index.