Add more heuristics to example search in collocationAnalysis

[kupietz]

See also:

@InProceedings{ELX08-026,
	   author = {Adam Kilgarriff, Miloš Husák, Katy McAdam, Michael Rundell, Pavel Rychlý, },
	   title = {GDEX: Automatically Finding Good Dictionary Examples in a Corpus},
	   pages = {425-432},
	   booktitle = {Proceedings of the 13th EURALEX International Congress},
	   year = {2008},
	   month = {jul},
	   date = {15-19},
	   address = {Barcelona, Spain},
	   editor = {Elisenda Bernal, Janet DeCesaris},
	   publisher = {Institut Universitari de Linguistica Aplicada, Universitat Pompeu Fabra},
	   isbn = {978-84-96742-67-3},
	}