operation-target should have different values

A the moment new parameter operation-target in host commands have values:

primary - query the primary source - JSON configuration.
alternate - query the alternate source - hosts database(s).
all - query both sources - JSON configuration and host database(s).
default - query the default source - it's command specific.

While situation when someone will use both database and file is rare (in my opinion, I don't have data) and current values of operation-target are intuitive for ppl that knows internals of how reservation works. I propose to change those values to something like:

memory (not json, because it's not saved) - query the primary source - JSON configuration.
database - query the alternate source - hosts database(s).
all - query both sources - JSON configuration and host database(s).
default - query the default source - it's command specific.

or something that would be easier to understand for anyone.