[update] ADD where RAW style

[phpseven]

before: when we use where RAW on SQL_FUNCTION(col_name), we must write whole condition in ONE RAW SQL,
now : You can write one condition in ONE RAW,

In other words, as long as there is an SQL method, all limit, order and group by must be written together. Not elegant

也就是说，之前只要带有一个sql的方法，那所有的LIMIT，ORDER，GROUP BY就都必须写在一起了，很难看

$data = $database->select('account', [
'user_id',
'email'
],
Medoo::raw('WHERE
LENGTH(<user_name>) > 5
ORDER BY RAND()
LIMIT 10
')
);

now you can write it like

$this->database->select(
"account",
"user_name",
[
Medoo::raw("ROUND(<float_val>) = :round_value", [':round_value'=>10]),
'LIMIT' => [20, 100],
"ORDER" => "user_id",
]
);