Fix of skills.json extractor.

It's a pull issue and bugfix same time.
Running lang/update_pot.sh right now return python traceback like this:
```
Traceback (most recent call last):
  File "lang/extract_json_strings.py", line 82, in <module>
    jsondata = json.loads(open(jsonfile).read())
  File "/usr/lib/python2.7/json/__init__.py", line 326, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
    obj, end = self.scan_once(s, idx)
ValueError: Expecting property name: line 7 column 5 (char 318)
UPDATE ABORTED`
```
Python json parser don't like commas after "description".
This branch fix that. +fix of python extractor script