fix error due to corrupted image, error due to empty pot
fixed plotting on top of image
Fix bug 120

* util/derandui.py (_addTS): Fix typos.
Make sure we ignore all utf-8 errors from csv file.

* util/derandui.py (_createDerandStruct, _addCsv): Use unicode(...,
errors="ignore") to make sure we can use str() on all strings. In the future we
might want to change all the str() into unicode()