Config-less server operation [gh-138] [gh-231]

Do not read or require tarantool.cfg. Accept all options
in the script itself. Split server reconfiguration so that
parts of the server can be reconfigured independently.
Remove dependency on confetti.

To configure the server at start, call

box.cfg{option1=value1, option2=value2}

To reset an option on the fly, do the same:

box.cfg{option=value1}

box.cfg is a Lua table with all existing options.

Make local hot standby the default and remove local hot
standby option [gh-231].
If neither primary nor admin port is specified, the server does
not get stuck in local hot standby mode, and becomes a master
immediately.

Incompatible changes:
- pid_file is nil by default, and the server does not create
a pid file by default.
- local_hot_standby option is removed
- log_level is now a dynamic option
- wal_mode is "write" by default
- box.cfg only prints non-nil options

Clean up a lot of garbage code in the test system.
Remove configuration file support from TarantoolServer
and Lua test preprocessor.

The patch also contains a few unrelated improvements in the
interactive mode (history support, ^D leads to exit).

@todo The patch disables region_gc in recovery, which
may lead to memory overconsumptions when recovering large
snapshots. This needs to be fixed separately.

@todo Remove all configuration files and confetti files
in a follow-up patch (not done in this patch to not clutter
it).