Add option to crush isolated bubbles

[jflot]

This should allow us to obtain a better level of continuity when assembling haploid genome (or diploid genomes with a very low level of heterozygosity).

[rotifergirl]

What is the best way to run the "haploid mode"? Do I enter the ploidy after -H?

[Malfoy]

This feature is currently not yet fully functional.