Upgrade to 1.554.2 to explicitly resolve an overload ambiguity

This PR has a handful of changes, but the primary intent is to change the groovy call to "getRelativeNameFrom" to "getRelativeNameFromGroup", which isn't available at 1.509.

Supplementary changes include:
1) Updating the LTS version on which we depend
2) Fixing a couple new findbugs warnings that fall out from #1
3) Updating a test, which was checking some literal text from the older core version.