renamed dig to digbc
Implemented SimilarityHistogram based clustering
added test for SHC
fixed bug in cluster assignment
Merge branch 'algo_compare' into digbc_clustering

Conflicts:
	core/digbc/__init__.py
	core/digbc/dig.py
	core/digbc/digbc.py
created parameterized clustering method for DIG SHC
added parameter grid for DIGSHC
smaller param grid for DIG SHC and some minor fixes
added caching of similarities
improved parameter values for DIG SHC, and also improved param grid values for next search
Merge branch 'digbc_clustering' into algo_compare

Conflicts:
	eval/__init__.py
* added phrase-based distance to DIG
* created stub for IHAC/DIG integration (vectorization vs. centers issue must be solved)