Expand fetch-fk-only to only automatically apply if recursionDepth is not set from default.

[andyjefferson]

If the user specifies fetch-fk-only on a 1-1/N-1 field any retrieval will always try to just pull back the FK value and no further. There is currently no way to overrule that metadata setting. Arguably people would be better advised to just use JDO standard "recursionDepth=0" to pull back the FK, but what we can do is to allow a user to specify recursionDepth as > 1 to overrule the fetch-fk-only setting.