Add compatibility adapters

[rjmholt]

PSSA2 will change some APIs but should continue to provide a way for users depending on the current PowerShell API structure to continue using those to offer a migration path where possible.

This includes:

• Providing objects with the same properties and methods as today's output objects
• Supporting legacy parameters on commands
• Allowing old-style configuration when flags are passed otherwise configured

[bergmeister]

What is the use case for that? The VS Code extension controls the version of PSSA anyway (other might have to implement their own control or move over to 2.0 quickly) and the point of the major version is to abandon concepts that are not useful.

[rjmholt]

Mainly for migration purposes. It's not a strong requirement. I just don't want to precipitously break everything, but rather provide a bridge for 1.x users.