Add ToFloat morphline

Very closely based on [ToString](https://github.com/kite-sdk/kite/blob/82d4d768267ca6e21cdced76d63fc9d0bf6a2fe3/kite-morphlines/kite-morphlines-core/src/main/java/org/kitesdk/morphline/stdlib/ToStringBuilder.java) builder. 

Not sure if conversion is done right, float constructor accepts:

```
Float(double value)
Float(float value)
Float(String s)
```

Perhaps I could just use casting it would automagically work?

@ljank