ReadTable should accept a path

[epineapple]

The ReadTable function currently expects to write a large file to the user's home directory. This interface should change (or a new interface added) to allow for the specification of a different directory. This makes sense for several reasons:

1. If LXRHash is used in a daemon or service, there may not be a home directory to use.
2. It would be nice to share these files between all users on a system.
3. The user may wish to store the file on a faster medium than that which stores the user's home directory.

I'm happy to submit a PR if one is welcome.

[Emyrk]

This is a valid request. I would not like to make a breaking API change.

We should create a new function that allows the change of the LXR hash table location. Perhaps even allow an environment variable to change the location so all applications will respect it?

[epineapple]

I would be open to an environment variable, e.g., LXRHASH_TABLEPATH. I also think that LXRHash should specify a shared system-wide location, such as /var/lib/LXRHash or /var/opt/LXRHash on *NIX, C:\ProgramData\LXRHash on Windows and /Library/Application Support/org.pegnet.LXRHash on macOS. This would make it easier for applications using LXRHash to select a common path.

[Emyrk]

Moving the location is reasonable, but we have already made docker containers and externals apps with the home path. I think adding an environment variable would be flexible. Any PR to do that would likely be accepted

[epineapple]

We can do an environment variable.

Just so you're aware of what that will mean for a Windows service using LXRHash, the service may need to have the environment variable set in the registry. If that's the case, then any changes will require a reboot. (I've not yet tested whether the service can simply set the environment variable once it starts, as a hacky way of passing the variable.)

https://docs.microsoft.com/en-us/windows/win32/services/service-startup