Fixed `yii\log\DbTarget` migration and SQLs to use float column for log_time

framework/log/migrations/m141106_185632_log_init.php

@@ -65,7 +65,7 @@ class m141106_185632_log_init extends Migration
                 'id' => Schema::TYPE_BIGPK,
                 'level' => Schema::TYPE_INTEGER,
                 'category' => Schema::TYPE_STRING,
-                'log_time' => Schema::TYPE_INTEGER,
+                'log_time' => Schema::TYPE_FLOAT,
                 'prefix' => Schema::TYPE_TEXT,
                 'message' => Schema::TYPE_TEXT,
             ], $tableOptions);

framework/log/migrations/schema-mssql.sql

@@ -19,7 +19,7 @@ create table [log]
    [id]          bigint IDENTITY PRIMARY KEY,
    [level]       integer,
    [category]    varchar(255),
-   [log_time]    integer,
+   [log_time]    float,
    [prefix]      text,
    [message]     text
 );

framework/log/migrations/schema-mysql.sql

@@ -19,7 +19,7 @@ create table `log`
    `id`          bigint(20) NOT NULL AUTO_INCREMENT PRIMARY KEY,
    `level`       integer,
    `category`    varchar(255),
-   `log_time`    integer,
+   `log_time`    float,
    `prefix`      text,
    `message`     text,
    key `idx_log_level` (`level`),

framework/log/migrations/schema-oci.sql

@@ -19,7 +19,7 @@ create table "log"
    "id"          number(20) NOT NULL PRIMARY KEY,
    "level"       integer,
    "category"    varchar(255),
-   "log_time"    integer,
+   "log_time"    float,
    "prefix"      text,
    "message"     text,
    key "idx_log_level" ("level"),

framework/log/migrations/schema-pgsql.sql

@@ -19,7 +19,7 @@ create table "log"
    "id"          bigserial NOT NULL PRIMARY KEY,
    "level"       integer,
    "category"    varchar(255),
-   "log_time"    integer,
+   "log_time"    real,
    "prefix"      text,
    "message"     text
 );

framework/log/migrations/schema-sqlite.sql

@@ -19,7 +19,7 @@ create table "log"
    "id"          integer PRIMARY KEY AUTOINCREMENT NOT NULL,
    "level"       integer,
    "category"    varchar(255),
-   "log_time"    integer,
+   "log_time"    float,
    "prefix"      text,
    "message"     text
 );