Adjust cache behavior for smoother rebuilding

[sbleon]

• Throw an error if misconfigured instead of logging. Also remove a maybe-lying comment.
• Replace the cache file after scanning for objects instead of blowing it away first thing

[Rodel30]

Good idea, just one little thing I think should be different 🙃

[Rodel30]

While I think the use case likely doesn't really exist, given the names of the arguments I think it may be better to have this as:

<cfif arguments.useCacheFile>
//Writing the cache file, as is currently happening
<cfelseif arguments.deleteCacheFile>
//delete the cache file without writing a new one, effectively moving the delete command that used to be up top down here
<cfelse>
//do nothing, as is currently happening

This preserves the previous effective functionality, while still having the benefit of not having a missing cache file while the new copy is being constructed.

[sbleon]

I'm intentionally changing the meaning of deleteCacheFile to be "replace cache file". Of the few known apps (2?) that use this library, I don't think there are any use cases that would just want to delete file and not replace it.