BUG: update RSS extension.

1. fix a bug: the mask image is not init-ed to all 0, which causes problem

2. clean up some debuging code
BUG: fix a bug in computing kappa in RSS
Merge pull request #447 from gaoyi/update-RSSExtension

BUG: Update rss extension
FIX: Fixed typo in header include which caused Linux build error
Merge pull request #448 from paulcm/update-LongitudinalPETCT

Fixed typo in header include