Investigate not Using ZK C Library

[tgockel]

The C library is fine for starters, but it might not be a great long-term solution.

• There is no way to implement Logging Hooks #21: The log_callback_fn has the signature void (*)(const char *message) with no way to associate a user context. This means we cannot do per-connection logging...or really anything but a global. This might be fine if the log callback function could be set without a zhandle (set via either zookeeper_init2 or zoo_set_log_callback)
• The watch callback code is horrendously hacky and probably not thread-safe. It might not leak memory, but the code is so damn convoluted it's hard to tell.
• All the adapter code looks horrible, but the transaction layer is especially bad.
• The connection interface described in AFIO-like connection interface #66 seems quite difficult/impossible to implement using the C library.
• It is the only dependency in the software.

Obviously, walking away from the battle-tested C library is a huge disadvantage here.