Revert "use sRGB colorspace instead of RGB in image conversion."

This reverts commit a407286805ed97387fbb0afa24d8c7c059bc72b0.
=> it makes test testERP5WebWithDms failing. Please update unit
test and also add test to check what you fixed with this change.
use sRGB colorspace instead of RGB in image conversion.

> Note, ImageMagick assumes the sRGB colorspace if the image format does not indicate otherwise.
http://www.imagemagick.org/script/command-line-options.php#colorspace

Also updated expected converted result with sRGB output.
Implement cache of getInventory results

Create a sql cache for getInventory call
Remove full-inventory optimisation as it now useless
Implement full-inventory feature directly into stock
Make erp5_pdm depends on this optimisation
Install optimisation for all unit tests
raise RuntimeError instead of Unauthorized for functional tests.

so that we will not have HTTP authentication dialog in case of  Unauthorized exception to prevent blocking in functional tests.
fix a typo in 83a7e9dfe0, sorry...
Merge branch 'master' into ivan_dms