Changed the public API

I was randomly using VPO and realized function names are a bit verbose, ie. `getValueByPath` can be just `get`.

At the same time I saw that set / get functions had inconsistent signatures:

* get: `obj, path`
* set: `value, path, object`

If we wanna keep the value as first argument of the setter, then I think we should still use the same order, for the order parameters, that is used in the getter, so `set(value, object, path)`.

I anyhow changed  it to `set(obj, path, value)` as - to me - it reads more natural. Let me know what you think.

Cheers!