Fix translateAndCapitalizeNamespaces for Portuguese

Per discussion on
https://secure.wikimedia.org/wikipedia/pt/wiki/Wikipédia:Esplanada/propostas/Incentivar_o_uso_de_"Imagem"_em_vez_de_"Arquivo"_ou_"Ficheiro"_(12mar2011)?uselang=en
please, change the function translateAndCapitalizeNamespaces (from cosmetic_changes.py) so that the bots stop doing the following chnges:
* Image --> Ficheiro
* File --> Ficheiro
* Arquivo --> Ficheiro
* Imagem --> Ficheiro

This is necessary in order to avoid linguistic problems, considering that "Arquivo" is the preferred word on Brazil but "Ficheiro" is preferred on Portugal.

For **image** files, the word "Imagem" is common to both Portuguese variants, and as such it is preferred, so this should be the name used when changing the namespace name of images. The use of "Ficheiro" and "Arquivo" is preferred only for **other kinds of files** (such as PDF or OGG), which are not images.

So, in short, the bots should do the following changes:
* For images (i.e. files with one of the following extensions: png, gif, jpg, jpeg, svg, tiff, tif), change:
** Image --> Imagem
** File --> Imagem
** Ficheiro --> Imagem
** Arquivo --> Imagem
*For other files (i.e. files with one of the following extensions: xcf, pdf, mid, ogg, ogv, djvu, oga):
** Arquivo --> Do not change (we should respect the variant used by the editors)
** Ficheiro --> Do not change (we should respect the variant used by the editors)
** File --> Do not change (or change randomly to "Ficheiro" or "Arquivo", since it is indeed a "file" and both pt and pt-BR are acceptable)
** Image --> Do not change (or change randomly to "Ficheiro" or "Arquivo", since it is indeed a "file" and both pt and pt-BR are acceptable)
** Imagem --> Do not change (or change randomly to "Ficheiro" or "Arquivo", since it is indeed a "file" and both pt and pt-BR are acceptable)

PS: the output of "python version.py" is the foolowing, although this bug report applies to all versions:
----
Pywikipedia [http] trunk/pywikipedia (r9323, 2011/06/30, 12:40:56)
Python 2.7.1+ (r271:86832, Apr 11 2011, 18:13:53)
[GCC 4.5.2]
config-settings:
use_api = True
use_api_login = True
unicode test: ok
----