Start a branch for easier OpenSSL configuration.
Employ config option for OpenSSL config file, if provided.
This should help make OpenSSL configuration on Windows servers easier by allowing the openssl.cnf file to be set directly in the ownCloud config, rather than in SetEnv commands that don't exist and are hard to replicate in IIS.
Don't cache the pkey, skip generation if the keyfile exists
This function doesn't cache anymore. Adjusted PHPDoc to suit.