Auto-update dictionary from mdbg.net

[larryk78]

Latest dictionary with regular (usually daily) updates is available for download at http://www.mdbg.net/chindict/export/cedict/cedict_1_0_ts_utf-8_mdbg.zip

Currently the way to update the dictionary in the app is for Larry to download it and manually construct/verify the indexes. Then release a new version of the app via the app store.

Add download and auto-indexing capability to Kuaishuo so that users can update the dictionary on their phone, without having to update the app.