bug-56: do the followings:

1. add download activity
2. add listadapter for language
3. change wordsstorage to support one db for a lang and category
combination.
4. add dialogutils
5. add errorutils
6. option dialog for partial downloaded db
Already fixed it. Please see the line 31 (https://github.com/Vosie/WikiCards/pull/15/files#diff-29c97ce97fa781e29588818081a69238R31)