hOCR files: Add XHTML header

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
hOCR files: Keep spaces between words

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
hOCR files: Add tag <br/> after each line

Signed-off-by: Jerome Flesch <jflesch@gmail.com>