Issue title: Does exist  any interface for create a database if not exist, and create a collection if not exist?
 Issue body: ## I need write check code when create a database and a collection as follows:
        if (!arangoDB.getDatabases().contains(DB_NAME)) {
	    arangoDB.createDatabase(DB_NAME);
	}

        try {
	    database.collection(ENTITY_COLLECTION).getInfo();
	} catch (ArangoDBException e) {
	    if (e.getMessage().contains("Response: 404")) {
	        final CollectionCreateOptions collectionOpt = new CollectionCreateOptions();
	        collectionOpt.numberOfShards(10);
	        collectionOpt.type(CollectionType.DOCUMENT);
	        database.createCollection(ENTITY_COLLECTION, collectionOpt);
	    } else {
	        e.printStackTrace();
	    }
	}
Is there any interface can do this just one call?
 Comments: 
 Comment 0: Hi,

there is no createIfNotExist for database or collection. The only you can do this with only one request is create the database/collection and catch the excpetion when it already exists.

```java
try {
  arangoDB.createDatabase(DB_NAME);
} catch (final ArangoDBException e) {
  // ignore if Response: 409, Error: 1207 - duplicate name
  if (!e.getMessage().equals("Response: 409, Error: 1207 - duplicate name")) {
    e.printStackTrace();
  }
}
```
 Comment 1: Thanks @mpv1989.  Will add createIfNotExist interface in the future?
 Comment 2: I have written it on my todo-list for future discussions. I cannot guarantee it.
 Comment 3: Thanks, i got it.
{'source': 'GithubIssues', 'repo_name_with_owner': 'arangodb/arangodb-java-driver', 'issue_id': 196598711, 'repo_stars': 210.0}