add shield 2.0.0-rc1 release notes
add shield 2.0.0-rc1 release notes

Original commit: elastic/x-pack-elasticsearch@22e6a1499f3c0548afd754bc35c23d6df26b7d46

coding0011/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,scorpionvicky/elasticsearch,strapdata/elassandra,gfyoung/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,gfyoung/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,strapdata/elassandra,robin13/elasticsearch,strapdata/elassandra,nknize/elasticsearch,uschindler/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,coding0011/elasticsearch,vroyer/elassandra,strapdata/elassandra,HonzaKral/elasticsearch,vroyer/elassandra,nknize/elasticsearch,robin13/elasticsearch,gfyoung/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,scorpionvicky/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,vroyer/elassandra,uschindler/elasticsearch,gfyoung/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,strapdata/elassandra,scorpionvicky/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,gfyoung/elasticsearch,HonzaKral/elasticsearch,scorpionvicky/elasticsearch