Add options to add a custom CA for secure connections

[lucmurer]

It is not always the case that internal devices have certificates signed by a global CA accepted by the host operating system that runs fotoobo.

So we should add options to the configuration / inventory to add custom CA certificates / known good certificate information:

• Add a custom CA to the inventory (or globally to fotoobo.yaml?)
• Perhaps give the possibility to provide the known good hash of the respective certificate per device in the inventory. -> Need to check, whether Python SSL/TLS support supports this...