Swap jvmcfg

With the addition of service-specific support in
`bin/omero config`, the previous jvmcfg naming
scheme of `omero.jvmcfg.$SERVICE.$PROPERTY` was
perhaps confusing. Now, the service name is parsed
from the end: `omero.jvmcfg.$PROPERTY.$SERVICE`.

*This will require a documentation update*

/cc @sbesson @manics

To test:
 * `bin/omero config omero.jvmcfg.perm_gen.blitz 2g` should do what previously the key `omero.jvmcfg.blitz.perm_gen` did.
 * Confirm with `bin/omero admin jvmcfg` command, and make any suggestions on the output style.