Refactorerd control functions to enable parallel blob classification

git-svn-id: http://tesseract-ocr.googlecode.com/svn/trunk@904 d0cd1f9f-072b-0410-8dd7-cf729c803f20
Added par_control.cpp

git-svn-id: http://tesseract-ocr.googlecode.com/svn/trunk@905 d0cd1f9f-072b-0410-8dd7-cf729c803f20