Including capability to localize EZFormStandardInputAccessoryView

Changed the hard-coded texts "Previous", "Next" and "Done" to get
values from NSLocalizedString. Also added example in EZFormDemo project
by localizing with Localizable.strings file (brazilian portuguese file
included)
Added descriptions and changing "Next" translation

As @jessedc suggested, added descriptions to NSLocalizedString to
Previous, Next and Done. Also, changed the portuguese translation of
Next, now it's the same as in Safari
Merge pull request #26 from allistoncarlos/master

Including capability to localize EZFormStandardInputAccessoryView