Adding interface to support validation of entire certificate chain

The interface added accepts a collectiong of certificates in PEM format and checks whether each certificate at i is issued by certificate at i + 1 and then checks the root certificate against the supplied list of CAs
Jira issue: WP-680
Fixing error with unparsed cert

Added parseCert on the root certificate which was omitted in earlier commit
Jira issue: WP-680
Merge pull request #7 from nix4/WP-680-embed-fokus-certificate

Add an interface to enable validation of certificate chains