Interface for Near-Duplicate detection libs

Added dependency for xxhashing, which will be used to hash features.
Moved files to a seperate package
Changes in StateVertexImpl to implement near-duplicates
Added tests for generateHash
Implementation of simha.. eh crawlhash
Added support for multiple feature-types
Make tests for the feature shingles
Add possibility to use different shingle sizes

The possible shingle sizes are now (n is some specified amount):
- n chars
- n words
- n sentences
Added strippers to strip the head and redundant whitespace
Implemented the new domstrippers
Tests for the hamming distance
Check for near duplicates on all vertices in the graph
Refactor tests for CrawlHash
Also fixes int long problem of the hashes
Put the threshold for the hd in the config

Compatibility fix for java 7. Integer.BYTES => 4
Insert hash in the results.json
Get the distance between two hashes
Added resetInstance-method to Singleton and fixes some bugs

Fixes threshold assignment bug fix

Prevent duplicate default features
Tests for the redundant whitespace stripper
Added getter for features
Tests for Broder's near duplicate detection
Implementation of Broder's ndd
Compatibility fixes for crawlhash and broder ndd
Add tests for to big feature sizes