KeyToMeta

A plugin for converting keys to metakeys
I think maybe. ret may be negative for two reasons: 

* If calloc failed, `elektraKsToMemArray` will return a negative value on NULL pointers. free won't hurt in this case (according to the doc: If ptr is a null pointer, no action occur)
* if calloc doesn't fail, but `elektraKsToMemArray` does (e.g. because returned is NULL for any reason), free will cleanup the allocated buffer

Am I missing anything?