[SPARK-16101][SQL] Refactoring CSV schema inference path to be consistent with JSON

## What changes were proposed in this pull request?

This PR refactors CSV schema inference path to be consistent with JSON data source and moves some filtering codes having the similar/same logics into `CSVUtils`.

 It makes the methods in classes have consistent arguments with JSON ones. (this PR renames `.../json/InferSchema.scala` → `.../json/JsonInferSchema.scala`)

`CSVInferSchema` and `JsonInferSchema`

``` scala
private[csv] object CSVInferSchema {
  ...

  def infer(
      csv: Dataset[String],
      caseSensitive: Boolean,
      options: CSVOptions): StructType = {
  ...
```

``` scala
private[sql] object JsonInferSchema {
  ...

  def infer(
      json: RDD[String],
      columnNameOfCorruptRecord: String,
      configOptions: JSONOptions): StructType = {
  ...
```

These allow schema inference from `Dataset[String]` directly, meaning the similar functionalities that use `JacksonParser`/`JsonInferSchema` for JSON can be easily implemented by `UnivocityParser`/`CSVInferSchema` for CSV.

This completes refactoring CSV datasource and they are now pretty consistent.

## How was this patch tested?

Existing tests should cover this and

```
./dev/change-scala-version.sh 2.10
./build/mvn -Pyarn -Phadoop-2.4 -Dscala-2.10 -DskipTests clean package
```

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16680 from HyukjinKwon/SPARK-16101-schema-inference.