support copy command

[lucasRogerioOliveira]

Support 'copy' command.

Actually, cassandra doesn't support rename table name, and to rename a table we need:

• migrate the data to a file or something like this with the command: 'copy';
• drop the table;
• recreate with the new name;
• use copy again to migrate the data from file to the renamed table;

Example:
-- description: recreate foobar table
-- authoredAt: lucasoliveiracampos
-- up:

-- stage: 1
copy foobar to 'foobar_2017_08_19_11_17_00_data.csv';

-- stage: 2
drop table foobar;

-- stage: 3
create table foobar (
foo text,
bar bigint,
primary key ((foo))
);

-- stage: 4
copy foobar from 'foobar_2017_08_19_11_17_00_data.csv';

-- down: