svd test case completed for now
refactoring : package renaming
refactoring matrix implementation for future optimization (lot of calls
to indexOf on ArrayList)
API of simuilarity package and first draft of implementation
package lsa API and first draft of implementation
javadoc update
SVD test added and bug identified
completed implementation for LSA
added a uniqueID to documents and tokens
refactoring matrix with reverse indexing using the unique ID
bug fix