Continue with lws_struct, add sqlite support for one
level of lws_dll2_t lists of structs serialization and
deserialization, plus the matching api-test.
Generic sessions has been overdue some love to align it with
the progress in the rest of lws.
1) Strict Content Security Policy
2) http2 compatibility
3) fixes and additions for use in a separate process via unix domain socket
4) work on ws and http proxying in lws
5) add minimal example
