Add functions to ask the macOS users to install the HTTPS certificates for Safari

[Xayton]

See the full description of the activity here: #907 and the corresponding comments.

• Add a way to prompt the user for confirmation (like a dialog window)
• Add a new setting installCertificates used to save if the user want's to install them or not (true, false, missing). If missing, the user should be prompted at the first check.
• Add some logic at startup, that will prompt the user if they want to install the HTTPS Certificates, explaining it's needed if they want to use the Agent with Safari.