Support for searching pattern in file

[stevie-sy]

trafficstars

This PR expand the check "Invoke-IcingaCheckDirectory" with a param to check also for patterns in files. If something is missed, pls let me know

[cla-bot[bot]]

Thank you for your pull request. Before we can look at it, you'll need to sign a Contributor License Agreement (CLA).

Please follow instructions at https://icinga.com/company/contributor-agreement to sign the CLA.

After that, please reply here with a comment and we'll verify.

Contributors that have not signed yet: @stevie-sy

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Please contact us if you think this is the case.

• If you signed the CLA as a corporation, your GitHub username may not have been submitted to us. Please reach out to the responsible person in your organization.