Allow importing and exporting the current Registry key value partially using the CLI.

[DrewNaylor]

The way this can be handled is, the helper program will accept a file path as an argument after /export, and the UI will offer a file browse dialog to select a folder to export to.

There can also be a /import command which also accepts a file path (with a file browse dialog provided by the UI for ease of use), and this one directly applies a Registry key value from a properly-formatted file as long as it has permission to do so.

These UI menu items can be Import directly to Registry from file and Export current Registry key value to file. Maybe adding a submenu for Import and Export would help it be a little less cluttered.