Remove AutoPropertyObject dependency on __init__

[feerrenrut]

Link to issue number:

No issue number.

Summary of the issue:

A class that inherits from AutoPropertyObject and does not (forgets to) call super in the __init__ function, would result in a failure for CachedGetter properties.
An example of this is BrailleBuffer

To reproduce the error, in the NVDA python console:

import braille
braille.handler.buffer.brailleToRawPos

gives:

braille.handler.buffer.brailleToRawPos
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "baseObject.pyc", line 34, in __get__
  File "baseObject.pyc", line 108, in _getPropertyViaCache
AttributeError: 'BrailleBuffer' object has no attribute '_propertyCache'

Description of how this pull request fixes the issue:

Create the _cachedProperties dictionary in the __new__function, this is always called automatically.
A missing super call on AutoPropertyObject children no longer causes failure for CachedGetter properties.

While here I noticed that there is the possibility that the generator expression for transforming the dictionary keys (such as _get_myVal, _set_myVal, and _del_myVal) would result in duplicates ("myVal" would be output 3 times). This results in unnecessary iterations of the loop that follows. Converting this to a set comprehension avoids that.

Testing performed:

Ran NVDA and ran the following in the NVDA python console without getting an error:

import braille
braille.handler.buffer.brailleToRawPos

Known issues with pull request:

None

Change log entry:

None

[derekriemer]

Might this hide any errors if the addon author orgets to call super in init

[feerrenrut]

If they are inheriting directly from AutoPropertyObject then there is now no risk to forgetting to call super. However, for other classes this danger essentially has not changed. Before this change, it was possible that everything would work correctly for most of the time. Only when get was called on specific objects (those that are cached) would the error show up. How this problem manifests really depends on the object and how it's used.