Support input deserialization from FileInfo objects

[BernieWhite]

Currently PSRule de-serializes YAML and JSON objects from string when the -Format parameter is used with Invoke-PSRule and Test-PSRuleTarget.

To read a YAML file from disk, Get-Content -Raw -Path path_to_file | Out-String needs to be used.

For example:

Invoke-PSRule -InputObject (Get-Content -Raw -Path path_to_file | Out-String) -Format Yaml;

Instead -InputObject should automatically read and deserialize the file contents of FileInfo objects when the -Format is used.

For example:

Invoke-PSRule -InputObject (Get-ChildItem -Path path_to_file) -Format Yaml;