Move to Crowdin platform

Notes:
* There are more languages on Crowdin than in the language option menu
* The languages order seems strange
* English folder is missing in Crowdin download (fix in crowdin not script)
* It might be possible to refactor pycurl dependency into urllib2
* mk1i18n will push new strings to translate generated by xgettext if there is a file named ```crowdin_api_key.txt``` in ```build/``` only containing a valid api key (about 20 digits)