Changing default Download location
Creating download location in Constants
Fix call requires api level 9 (current min is 7) java.text.normalizer#normalize

In order to use normalize we need API >= 9. We've added a check, but it is neccesary
to add a fallback code for all devices with API < 9
Fixing downloads path
Do not re-download downloaded files fully working

If user try to download a file that is already downloaded, avoid the conexion and
open the local file (Only if the file is the same and has not changed its contents).

If there is not local file, download it.