box: user-friendly interface to manage ck constraints

Closes #3691

@TarantoolBot document
Title: check constraint for Lua space

The check constraint is a type of integrity constraint which
specifies a requirement that must be met by tuple before it
is inserted into space. The constraint result must be predictable.
Expression in check constraint must be <boolean value expression>
I.e. return boolean result.

Now it is possible to create ck constraints only for empty space
having format. Constraint expression is a string that defines
relations between top-level tuple fields.
Take into account that all names are converted to an uppercase
before resolve(like SQL does), use \" sign for names of fields
that were created not with SQL.

The check constraints are fired on insertion to the Lua space
together with Lua space triggers. The execution order of
ck constraints checks and space triggers follows their creation
sequence.

Note: this patch changes the CK constraints execution order for
SQL. Previously check of CK constraints integrity was fired before
tuple is formed; meanwhile now they are implemented as NoSQL before
replace triggers, which are fired right before tuple insertion.
In turn, type casts are performed earlier than msgpack
serialization. You should be careful with functions that use
field types in your check constrains (like typeof()).

Consider following situation:
```
 box.execute("CREATE TABLE t2(id  INT primary key,
                              x INTEGER CHECK (x > 1));")
 box.execute("INSERT INTO t2 VALUES(3, 1.1)")
```
the last operation would fail because 1.1 is silently
cast to integer 1 which is not greater than 1.

To create a new CK constraint for a space, use
space:create_check_constraint method. All space constraints are
shown in space.ck_constraint table. To drop ck constraint,
use :drop method.

Example:
```
s1 = box.schema.create_space('test1')
pk = s1:create_index('pk')
ck = s1:create_check_constraint('physics', 'X < Y')
s1:insert({2, 1}) -- fail
ck:drop()
```