Fix: Regression for negative proposal lines.

Conflicts:
	htdocs/comm/propal.php
fix wrong value name when updating buyingprice
Fix: Usage of order into export broken when filters are used
Merge pull request #727 from cbattarel/3.3

fix wrong value name when updating buyingprice
Merge remote-tracking branch 'origin/3.3' into develop
Merge branch 'develop' of https://github.com/Dolibarr/dolibarr.git into develop
Merge remote-tracking branch 'origin/3.3' into develop