add possibility to look for iron.json in parent directories

Add possibility to look for iron.json in parent folders.

It's needed for publishing to maven: maven takes source from git and this source hasn't iron.json file. So one possible way is to place iron.json in ../../ folder and let Client in unit-tests to search for it in parent directories.

```java
int level = 2;  // equivalent of ../../
int apiVersion = 3;
client = new Client(null, null, null, apiVersion, level);
```

This feature does not violate the existing interfaces.