[DEV-12] Honor DNS ttl in jsonrpc module

This is a big one. Some highlights:

- TTL is checked managed using a SIP-Router timer
- global_server_group is updated by sending commands to the IO process
- Added two IO commands, 'close' and 'connect'
- SRVs are tracked using an srv_list.
- A lot of stuff is now in shared memory
- Rename pkg_strdup to shm_strdup and removed the only shm_strdup
[DEV-12] Add module param "min_srv_ttl"
Fork timer process only in main.
[DEV-12] Honor DNS ttl in jsonrpc module

This is a big one. Some highlights:

- TTL is checked managed using a SIP-Router timer
- global_server_group is updated by sending commands to the IO process
- Added two IO commands, 'close' and 'connect'
- SRVs are tracked using an srv_list.
- A lot of stuff is now in shared memory
- Rename pkg_strdup to shm_strdup and removed the only shm_strdup
[DEV-12] Add module param "min_srv_ttl"
Fork timer process only in main.
Unbreak cmd_pipe for DNS timer.
Merge branch 'dns_timer' of github.com:flowroute/kamailio-jsonrpc-module into dns_timer

Conflicts:
	jsonrpc_mod.c
Merge pull request #9 from flowroute/dns_timer

[DEV-12] Honor DNS ttl in jsonrpc module