Update comments to better match Javadocs from ZXing

Also rename constants to include "ZX_" prefix
Various speed improvements

Most of these are due to removing unnecessary method calls for
properties.
Rename ZXHighLevelEncoder to ZXDataMatrixHighLevelEncoder
Ported r2834 from ZXing

Original commit message: "Aztec updates from fyellin"
Ported r2841 from ZXing

Original commit message: "Fix parsing of '12756.501'"
Ported r2846 from ZXing

Original commit message: "Issue 1738 Add support for margin hint in
PDF417"
Ported r2847 from ZXing

Original commit message: "Issue 1737: Add hint to not strip Codabar
start/end"
Ported r2850 from ZXing

Original commit message: "Issue 1742 fix back-tick in text encodation
set"
Ported r2852 from ZXing

Original commit message: "Allow less quiet zone to start an ITF barcode
when it is near the edge"
Ported r2862 from ZXing

Original commit message: "More misc inspection stuff"
Ported r2866 from ZXing

Original commit message: "Issue 1758 correct corner case of mask pattern
penalty 3"
Ported r2867 from ZXing

Original commit message: "Issue 1758: revert last change, applying
penalty at edge is necessary. Try new change from original code to avoid
applying in the "2 1 3 1 1" case"
Correct ZXMaskUtilTestCase
Ported r2870 from ZXing

Original commit message: "Issue 1762 PDF417 speed up and back-port to
Java"
Ported r2871 from ZXing

Original commit message: "Issue 1736 reject UPC/EAN less than 8 chars"
Ported r2873 from ZXing

Original commit message: "Issue 1758 try again with better rule
implementation that counts all exterior regions as white"
Ported r2875 from ZXing

Original commit message: "Issue 1764 bit reverse speedup"
Ported r2876 from ZXing

Original commit message: "Type weakening and dead code commenting again"
Updated AUTHORS file
Ported r2886 from ZXing

Original commit message: "Issue 1776 fix bad location of Code 39 end
pattern when followed by lots of white space"