Artifactory set and delete properties support

Dear Konstantin,

I have implemented Artifactory set and delete properties support. Please review.

Regards,
    Gabor
Please add a property setter using python decorator syntax:

```python
@properties.setter
def properties(self, value):
    ...
```

Call the set_properties with recursive=False from there

Also, make sure you handle the 
```python
path.properties = None 
```
or
```python
path.properties = {}
```

The reason is to have a relatively simple syntax of getting/setting/deleting properties on a single file, while also providing 'advanced' getter/setter functions that provide additional capabilities