Revert "Update POM version numbers to 5.0.0-rc2"

This reverts commit ceb3c487984ba48b210af85cfd97c65ed0f7a540.  The version numbers are now back to ```5.0.0-DEV``` and ```5.0.0-SNAPSHOT```.

This should be merged before other dev_5_0 PRs (so that we do not have multiple 5.0.0-rc2 builds).