Update the test after #1219 - proper removal of servers

* Don't print information if nothing has changed
* Remove -DENABLE_BUNDLED_XXX options which doesn't work
* Use common names for _DIRS and _LIBRARIES variables

Other changes:

 * Move CJSON sources to libserver to resolve dependency on lua/utils.c

Revised the entire tutorial (file help_en_US.lua):
 * Tested and fixed all sample code snippets.
 * Corrected typos and inconsistent names in screen headers.
 * Updated info about custom delimiters (screen #6).
 * Replaced box.session with fiber (example on screen #10).
 * Swapped screens #11/#12 (fibers/sockets) for smoother story flow.

Removed help-related stub logic (file help.lua).

Updated auto-tests to expect a new output result on help call.

too_long_threshold was used uninitialized in txn_write_to_wal()
during box_init().

* Use statically allocated non-buffered ipc_channel
* Replace ipc_channel_is_full() with ipc_channel_has_readers()

too_long_threshold was used uninitialized in txn_write_to_wal()
during box_init().

This patch also enables daemon supervision when used with systemd.
A prerequisite for Fedora/EPEL7 packages.

See https://github.com/tarantool/build/issues/10