Fix the syncronize button.

1) If you don't has a SDCard, when you click this button, the app will break.

2) If you has music files in "Music" folder and another one, the app will break too.
Because the processFiles method get a file list as parameter (actually search only Music
folder), but it's redo the search in SDCard full.

Now, the processFiles just process the file list parameter.

This patch fix these two cases. It uses the MetadataRetriever class, so
the minSdkVersion is 10, for now.
We dont have any doc.

Now, we have. :D
I added docs folder with some UML diagrams.
See docs/README for details.
Merge pull request #14 from adorilson/add_docs

We dont have any doc.
Merge pull request #13 from adorilson/fix-synchronize

Fix the syncronize button.
Add pt_BR translation
Translate context menu options
Merge pull request #15 from adorilson/add_ptBR

Add pt br translation.