Separate CAs for client certs and server cert chain

- Modified the VirtualHost screen to make more clear the difference between "server certificate chain" and "client certification authority"
- Modified configuration generation accordingly with proper options (SSLCertificateChainFile for server cert chain, SSLCACertificateFile for client certificates) according to Apache documentation
Merge pull request #576 from darksoul42/master

Separate CAs for client certs and server cert chain