Write errors in the similarity matrix to a file

Added writeSimilarityError function
Changed the similarity formula (totalIVforCommonWords)

Instead of doing 2*uniqueIVForCommonA we now do uniqueIVForCommonA +
uniqueIVForCommonB
Created main.h + better debug for sim matrix

Changed notation of d_sim indexes
rewrote printSimilarityDebug
added function to print documentIDs
Added comments to certain functions