Fix off-by-one in LZW decoding

See
http://lists.openmicroscopy.org.uk/pipermail/ome-users/2014-July/004566.html
One more indexing fix for LZW
ND2: ignore all blocks of image offsets except for the last one

Extra, possibly invalid, planes are sometimes stored before the first
true image in the dataset.  We now do what NIS Elements does, and ignore
everything except for the last continuous block of image offsets.

See
http://lists.openmicroscopy.org.uk/pipermail/ome-users/2014-July/004589.html
ND2: adjust default buffer size to speed up initialization

See http://trello.com/c/1ZClsqPU/42-nd2-performance
Merge pull request #1224 from melissalinkert/rebased/dev_5_0/lzw-fix

Fix off-by-one in LZW decoding (rebased onto dev_5_0)
Merge pull request #1226 from melissalinkert/nd2-final

Final .nd2 fixes for 5.0.3