Update PSC.md after PSC meeting (2018-02-22) :  new rules to accept Merge Request
Update PSC.md after PSC meeting (2018-02-22) : 
new rules to accept Merge Request
orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB