Document the need to use metaspace with OpenJDK 1.8

[#60250292]
Merge 60250292-java8-but-permgen to master

[#60250292]
Revert "[#60250292]test"

This reverts commit eed077949c7ce2df97a510e90aafe1701a0ee9d6.
Bump new-relic to 3.1.+

[#58173176]