Returning tests to their previous place. Fixing error in tarantool_connection, that prevernts reconnection. Fixing bug in cas.test

secondary_indexes_enabled.

Conflicts:
	src/box/tree_index.cc

calls.

Use beginBuild(), reserve(), endBuild() to implement Index::build().
This is a pre-requisite for the refactoring of the
recovery API to make recovery of data dictionary spaces more
straightforward.

@todo: manage instances in /etc/tarantool

Split key part allocation and initialization in key_def_create().
This makes it possible use of the same key_def_create() when
"building" a key def for memcached space, and when building
it from the configuration file.

Make key_def.[h,cc] unaware of struct tarantool_cfg.

Instead of populating Lua box.space[] table once at
server start, update it with space data whenever it changes.
This is a pre-requisite patch for the new data dictionary,
which allows adding/dropping spaces on a running server.

Generalize session triggers to be usable for on_commit/on_rollback
events.