Makes providing new-style masks easier

Adds ability to pass in new-style masks without mask[...] or begins with 'mask.'

All of the following examples are usable:
```python
# Old style
ticket = client['Ticket'].getObject(
    id=123456, mask="mask[updates, assignedUser, attachedHardware.datacenter]")
```

```python
# Old, with maskdot
ticket = client['Ticket'].getObject(id=123456, mask="mask.updates")
```

```python
# Without mask[...]
ticket = client['Ticket'].getObject(
    id=123456, mask="updates, assignedUser, attachedHardware.datacenter")
```