Initial SSL commit (WIP)

This commits the basic SSL functionality needed for the library.

Change-Id: I599bb6a883263e1889c2a87ae423684cd209d1e7
Refactor and fork vbucket

- Rewrite vbucket.c to be cleaner
- Add simple unit test
- Move header files into <libcouchbase/*>
- Mode source files into src/
- Add support for SSL ports (as of 3.0.0-367)

Change-Id: I277ef1e540556fd6c88fe00c09d1fc0709439f9b
Add additional set_nodes/get_nodes functions

These functions will allow to configure a provider with a specific list
of nodes, and retrieve the current node list.

Change-Id: Iba94fe73a8b4328039f1fcdf8fcd31ad20019fd8
Core settings integration for SSL

- Support for adding SSL options via lcb_cntl()
- Add SSL-related fields to lcb_settings
- Add (currently undocumented) LCB_FORCE_SSL environment variable to
  test behavior
- Add SSL 'protocol context' to lcbio
- bc_cccp, mcserver, and http are SSL aware in that they will select the
  SSL URIs/hosts if enabled

Change-Id: I0ea47e3ab824156e9456391aa60f5f5867086f61
Add LCB_ESOCKSHUTDOWN error code for EOF/graceful close

Change-Id: If7183974f1685395d4a35b9f935ed0717b305970
http: don't refresh config on graceful shutdown

Change-Id: Ib18a9ca0b5f353fae183cf1b53be398dcb758b12