Added new and updated translations, added transifex config, changed readme

+ added more translations by [Projectfork Translation Team](https://github.com/projectfork/Projectfork/wiki/Translation-Teams) (german, thai, catalan, etc...)
+ added languagetags to related xml-files
+ updated translation files from transifex (minor binary changes, for autocheck if something has changed)
+ added .tx transifex config to use with transifex client (instructions on how to use tx-client in wiki)
+ renamed readme file to use markdown code
+ added .gitignore to prevent unwanted commits (such as the tx.exe or mac/win crap)
+ remove double string from admin en-GB.com_projectfork.ini

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.gitignore and tx-config have to be updated again if further languages are added, etc...