Ignore text nodes when parsing XMLAnnotation's value

This fixes an error parsing Modulo annotations
(e.g. FLIM-modulo-sample.ome.tiff) in Matlab.
Fix tiled TIFF saving when partial tiles will be used

If the image width and/or height are not multiples of the tile
dimensions, then the last tile in each row or column will be smaller
than the others.  This commit prevents an exception when that is the
case.
Restrict direct tile copying to single-tile images
merge dev_5_0 -D org -I include -E exclude: PR 867 (Ignore text nodes when parsing XMLAnnotation's value (rebased onto dev_5_0))
merge dev_5_0 -D org -I include -E exclude: PR 871 (Fix tiled TIFF reading and writing)