Add ALTER TABLE ... RENAME TO ...

[yaziine]

This is a sub-issue of #94 that focuses on renaming an existing table.

We should be able to do the following:

genji> CREATE TABLE foo;
genji> INSERT INTO foo VALUES {name: "John Doe"};
genji> ALTER TABLE foo RENAME TO bar;
genji> SELECT * FROM bar;
{
  "name": "John Doe"
}
genji> SELECT * FROM foo;
table not found

If the table bar already exists, we should return an error.

[yaziine]

After reflexion I think that we need to change how the db is structured to handle the renaming of a table.

Currently, how the DB is structured forces us to duplicate all documents of a given table if we want to rename it.
Time complexity: O(n) and Space complexity O(n) as well.

What I suggest is to break the actual DB schema to save some complexity if we want to rename a table.

_genji.tables:
          foo: {store: 123abc, config: 456def},
          bar: {store: 111aaa, config: 789ghi}
123abc: <table's content>
111aaa: <table's content>

That way we can rename a table in a constant time (O(1)) because we only need to change the name of the table in _genji.tables store.
The store allows us to have a reference to the content of the table. We can use an uuid for generating the store value.