Add an INFO information element to export flow info without the need of plugins

[simonemainardi]

It would be desirable to have an %NTOPNG_ENTERPRISE_INFO IE containing information which is similar to the wireshark INFO column or the ntopng INFO column. Such IE would contain nDPI-provided data:

• The host name for HTTP flows
• The DNS query for DNS flows
• the SNI for TLS flows

etc.

This can be used to populate ntopng fields without the need to enable nProbe plugins and having independent IEs now listed in @NTOPNG@ template.

To cleanup, it would be nice to have nDPI generating this column, so that it can be unified with method Flow::getFlowInfo of ntopng.

[lucaderi]

Implemented in %L7_INFO