Ignore unprocessed objects by default

[BernieWhite]

Currently the Test-PSRuleTarget returns $True (fails open) if no rules matched the object (Outcome of None).

Originally when either $True or $False were the only output this seemed the best choice. Specifically:

The object fails if:

• Any rules fail or error.
• Any rules are inconclusive.

The object passes if:

• No rules were found that match preconditions, name and tag filters.
• All rules pass.

With #176 and #317 it no longer makes sense to return $True by default when the object hasn't even been processed.

Instead by default Test-PSRuleTest should:

• Return $False if any rule failed, returned an error or were inconclusive.
• Return $True if all rules passed.

Additionally an -Outcome parameter could be added to include None on an as needed basis.