Fix #691

Please, do not merge this yet; it is not finished yet, but this way anyone can start reviewing.

In this pull request I fix every existing PEP8 issue of openspending, issue #691, as found by PyCharm software.

I *do not* fix every issue PyCharm reports as it would change interface or others. Every change in this pull request is either formatting or within a very limited scope. In particular:

Changes in formatting:
- 2 lines distance between definitions
- 1 line in the end of file
- removed unused "/" inside brackets, etc.
- [ foo for foo in bar ] -> [foo for foo in bar]
- a == b -> a==b
- def f(arg1 = 2) -> f(arg1=2)
- etc

Changes within a very limited scope:
- dict.has_key(key) -> key in dict
- foo == None -> foo is None
- removed unused imports
- removed mix of tabs with spaces
- etc

I divided each python package in a different commit so they can be added in steps without any collision between them.

During this issue, I found other issues that could be dealt in a near future. Those include mutable default arguments, unused arguments, unused local variables, etc. I will try to create a detailed report in the mailing list, if you think it is worth doing it.

Finally and most important, overval, the code was very clean. A Big congratulations to all contributors; it is a pleasure to read the code.