Fix `fix` command to handle `--fixers` option when contains extra and excluding fixers

Currently, when `--fixers` option contains extra and excluding mixed filters such as `-eol_ending,concat_with_spaces`, excluding filter will be enabled, however, extra filter will not be enabled.

This PR fixes this behavior, so enable both type filters when mixed filters given.

----

`sample.php`

```php
<?php
echo 'foo'.'bar', PHP_EOL;

```

Current version: (`concat_with_spaces` is not enabled)

```
% php-cs-fixer fix -v --diff --fixers="-eol_ending,concat_with_spaces" --dry-run sample.php   
   1) /home/fivestar/sample.php (eof_ending)
      ---------- begin diff ----------
      --- Original
      +++ New
      @@ @@
       <?php
       echo 'foo'.'bar', PHP_EOL;
       
      -
      
      ---------- end diff ----------
```

Fixed version: (`concat_with_spaces` is enabled)

```
% php-cs-fixer fix -v --diff --fixers="-eol_ending,concat_with_spaces" --dry-run sample.php 
   1) /home/fivestar/sample.php (eof_ending, concat_with_spaces)
      ---------- begin diff ----------
      --- Original
      +++ New
      @@ @@
       <?php
      -echo 'foo'.'bar', PHP_EOL;
      -
      +echo 'foo' . 'bar', PHP_EOL;
       
      
      ---------- end diff ----------
```
No comments here, so if I am wrong please correct me.
We have configLevel, configFixers, optionLevel, optionFixers.

If optionFixers is set we take it, if not we take configFixers. Great.

If optionLevel is set we take it. Great.
If optionLevel is not set and fixerOption is not set then we take configLevel. Great.
If optionLevel is not set and fixerOption is set - why we take configLevel if _any_ of fixerOption is exclusion?

If I use `--fixers=aaa,-bbb,ccc` what fixers will be used?
All with default level (SYMFONY) without bbb but with aaa & ccc?

If I use `--fixers=aaa,ccc` what fixers will be used?
Only `aaa,ccc` (Without using all fixers at SYMFONY level)?



If I am reading it correctly then this will be cool ;) But it will be also worth to write it down in readme as well.