HPCC-11764 Dafilesrv authentication and encryption on transport

Current dafilesrv uses unencrypted sockets which is not secure. This update
adds a new section to the environment.conf file to optionally specify that
dafilesrv and its clients should use SSL, and points to the cert and key
files.
If specified, dafilesrv and its clients
will enable secure sockets (openSSL) and communicate in a secure manner.

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>