Ported r2569 from ZXing

Original commit message: "Issue 572 port of Data Matrix encoder from
barcode4j, adapted for Android, ported by Guillaume Le Biller and
stoty47 and adapted a bit more by me"
Ported r2572 from ZXing

Original commit message: "Doc an old ByteMatrix method in response to an
SO question"
Ported r2573 from ZXing

Original commit message: "URL-decode email address in mailto: link"
Ported r2574 from ZXing

Original commit message: "Issue 1604 Add LuminanceSource.invert()
method"
Ported r2576 from ZXing

Original commit message: "Better take on InvertedLuminanceSource --
allow possibility of rotation and efficient un-inversion"