Add localization to the client (translations)

[marcusmoller]

I just recently added support for localizations using the gettext module from Python. See: ee6d690

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I haven't finished making all the strings in the application into gettext-strings, so that should be done first of all.
This is done by simple adding the _( prefix and )suffix to strings.

An example: "This is a string in Python" becomes _("This is a string in Python!").

When all that is done, it's time to translate the strings into new languages.

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I have added two tools for making it easier to create the .po files for translations.

• https://github.com/marcusmoller/pyorpg-client/blob/master/tools/create-po.sh will search for all gettext-strings in the source code and create a messages.po which allows for easy translating.
• https://github.com/marcusmoller/pyorpg-client/blob/master/tools/convert-po.sh converts the created AND TRANSLATED messages.po from src/ into a .mo-file which is then able to be read by the client. Please note that you should edit convert-po.sh so that it's not ouputting messages_en.mo but rather you localization of choice, say messages_de.mo.