Gradle migration: use system property for nexus credentials (to retrieve them from Jenkins)
Gradle migration: use system property for nexus credentials (to retrieve them from Jenkins)

Change-Id: Id45e037d890966440ed641a60e72adadddd5c355

laurianed/scheduling-portal,lpellegr/scheduling-portal,paraita/scheduling-portal,ShatalovYaroslav/scheduling-portal,laurianed/scheduling-portal,lpellegr/scheduling-portal,sandrineBeauche/scheduling-portal,laurianed/scheduling-portal,sandrineBeauche/scheduling-portal,ow2-proactive/scheduling-portal,ShatalovYaroslav/scheduling-portal,ow2-proactive/scheduling-portal,ow2-proactive/scheduling-portal,paraita/scheduling-portal,lpellegr/scheduling-portal,paraita/scheduling-portal,sandrineBeauche/scheduling-portal,ShatalovYaroslav/scheduling-portal