[angel] rewrite parser, changing syntax (similar to main config)
[common] remove hash value type (use key/value lists instead)
[angel] rewrite config handling, rename items, document it

  * remove "instance { ... }" wrapping
  * use "_" instead of "-"
  * modules -> modules_path
  * allow_listen { ip "..."; } -> allow_listen_ip "...";
  * allow_listen { unix "..."; } -> allow_listen_unix "...";
[angel] merge allow_listen_* items

 * allow_listen_ip ".." -> allow_listen ".."
 * allow_listen_unix ".." -> allow_listen "unix:.."
 * allow_listen also takes lists of strings
[ip-parser] allow [ipv6]/net:port and [ipv6/net]:port for IPv6 address + network + port
[core] convert all assert() to LI_FORCE_ASSERT(), and support writing backtraces on fatal errors with libunwind