bump core version to 5.8.4-pre3
bump core version to 5.8.4-pre3

Terracotta-OSS/terracotta-platform,chrisdennis/terracotta-platform,albinsuresh/terracotta-platform,albinsuresh/terracotta-platform,Terracotta-OSS/terracotta-platform,chrisdennis/terracotta-platform