Update UI in accordance with Android design guidelines
Use flexible height for db_label

Text can be quite long (more than two lines) in some translations.
Use ImageButton instead of Button with "Default" label

Translation of "Default" can be quite long while horizontal space is
very limited on a phone screen.
Remove "Default" button text since it is not used anymore
Merge pull request #5 from relan/master

Update UI in accordance with Android design guidelines