**Describe the bug**
When using the HTTP protocol with DateTime64 types, numerical timestamps in milliseconds do not parse correctly. This is an issue when using the Clickhouse JDBC driver with Avro Kafka records because the timestamps are integers. 

**How to reproduce**
I'm using the following CH version: yandex/clickhouse-server:20.4.5.36

Create a sample table with: 
```sql
create table tst(ts DateTime64(3)) engine TinyLog();
```

Attempt to insert millisecond timestamp into the column:
```bash
echo "1596215121682" | http -v :8123 query=="insert into tst format TSV"
```

Error:
```bash
Code: 27, e.displayText() = DB::Exception: Cannot parse input: expected '\n' before: '682\n': (at row 1)

Row 1:
Column 0,   name: ts, type: DateTime64(3), parsed text: "1596215121"
ERROR: garbage after DateTime64(3): "682<LINE FEED>"

 (version 20.4.5.36 (official build))
```

Oddly, specifying a raw query, this works:
```bash
echo 'insert into tst values(1596215121682)' | curl 'http://localhost:8123/' --data-binary @-
```
Result:
```bash
SELECT *
FROM tst

┌──────────────────────ts─┐
│ 2020-07-31 17:05:21.682 │
└─────────────────────────┘
```



**Expected behavior**
I expect to be able to insert integer millisecond timestamps using the HTTP batch insert protocol. 

Again, this issue is preventing us from using the Clickhouse JDBC driver because it fails to parse our Avro records from Kafka.

Appreciate the help!

{
        if (from < 0)
            return 0;
        return from;
    }
};
/** Special case of converting Int8, Int16, (U)Int32 or (U)Int64 (and also, for convenience,
  * Float32, Float64) to Date. If the number is negative, saturate it to unix epoch time. If the
  * number is less than 65536, then it is treated as DayNum, and if it's greater or equals to 65536,
  * then treated as unix timestamp. If the number exceeds UInt32, saturate to MAX_UINT32 then as DayNum.
  * It's a bit illogical, as we actually have two functions in one.
  * But allows to support frequent case,
  *  when user write toDate(UInt32), expecting conversion of unix timestamp to Date.
  *  (otherwise such usage would be frequent mistake).
  */
template <typename Name> struct ConvertImpl<DataTypeUInt32, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeUInt32, DataTypeDate, ToDateTransform32Or64<UInt32, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeUInt64, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeUInt64, DataTypeDate, ToDateTransform32Or64<UInt64, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeInt8, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt8, DataTypeDate, ToDateTransform8Or16Signed<Int8, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeInt16, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt16, DataTypeDate, ToDateTransform8Or16Signed<Int16, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeInt32, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt32, DataTypeDate, ToDateTransform32Or64Signed<Int32, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeInt64, DataTypeDate, Name, ConvertDefaultBehaviorTag>