SkipClient error while parsing with recommended syntax in studio

Hello,

I want to use the skipClient. Based on issue #10 it should be supported.
When I use it like that (with for all)
and when I import it with `jhipster import-jdl jhipster-jdl.jh` I get the following error:
```sh
The JDL is being parsed.
error: Error message:
NoViableAltException: Expecting: one of these possible Token sequences:
1. ['@']
2. ['entity']
3. [COMMENT, 'entity']
4. ['relationship']
5. ['enum']
6. ['dto']
7. ['paginate']
8. ['service']
9. [COMMENT]
10. ['microservice']
11. ['search']
12. ['skipClient']
13. ['skipServer']
14. ['angularSuffix']
15. ['noFluentMethod']
16. ['filter']
17. ['clientRootFolder']
18. ['application']
19. [NAME]
but found: 'all'
at line: 10, column: 16
```
So I tried like that:

and in that case it works but there is a warning message in the studio.
Here is my jhipster version:

```sh
Executing jhipster:info
Options: from-cli: true
Welcome to the JHipster Information Sub-Generator

##### **JHipster Version(s)**

```
/home/djay
└── generator-jhipster@5.3.4

```

##### **JHipster configuration, a `.yo-rc.json` file generated in the root folder**

.yo-rc.json file

{

  "generator-jhipster": {

    "promptValues": {

      "packageName": "com.mycompany.myapp",

      "nativeLanguage": "en"

    },

    "jhipsterVersion": "5.3.4",

    "applicationType": "monolith",

    "baseName": "srv1",

    "packageName": "com.mycompany.myapp",

    "packageFolder": "com/mycompany/myapp",

    "serverPort": "8080",

    "authenticationType": "jwt",

    "cacheProvider": "ehcache",

    "enableHibernateCache": true,

    "websocket": false,

    "databaseType": "sql",

    "devDatabaseType": "h2Disk",

    "prodDatabaseType": "postgresql",

    "searchEngine": false,

    "messageBroker": false,

    "serviceDiscoveryType": false,

    "buildTool": "maven",

    "enableSwaggerCodegen": false,

    "jwtSecretKey": "bXktc2VjcmV0LXRva2VuLXRvLWNoYW5nZS1pbi1wcm9kdWN0aW9uLWFuZC10by1rZWVwLWluLWEtc2VjdXJlLXBsYWNl",

    "enableTranslation": true,

    "nativeLanguage": "en",

    "languages": [

      "en"

    ]

  }

}

##### **JDL for the Entity configuration(s) `entityName.json` files generated in the `.jhipster` directory**

JDL entity definitions

entity Region {

  regionName String

}

dto Region with mapstruct

service Region with serviceImpl

##### **Environment and Tools**

openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)

git version 2.18.0

node: v8.11.4

npm: 6.4.1

yeoman: 2.0.4

yarn: 1.9.4

Docker version 18.06.1-ce, build e68fc7a215

docker-compose version 1.22.0, build f46880fe

Congratulations, JHipster execution is complete!
```

Let me know if you need something else.