Split layer and client tools in packages

That is, remove them entirely from the deb and rpm, as client-tools only variants of those already exist, and allow them to be separately installed in the exe and pkg.

Really just shuffling what was already there to allow easier compartmentalization.

The only snag was if the FoundationDB Client isn't present. That's plausible if this a machine that will only contain a SQL app, for example, so the installers need to allow that. This is handled with a simple alert box from the exe. That isn't possible, outside of a custom Object-C plugin, in the pkg environment so (grudgingly) just add more text to the read me and description.