Speedup and memory improvement of global algorithm

[OndrejSladky]

• The global algorithm now first computes simplitigs (which is equivalent to merging on extensions of length 1) and the continues with the original implementation of greedy.
  • Preliminary results on s.pneumo genome:
    • ~4x speed up
    • ~3x memory savings
• Additionally, KmerCamel now prints indicator progress.

The algorithm remains the same, but due to (possibly) different tie-breakings, the results may differ.

[PavelVesely]

To make it even better, and add the icing on the cake, it'd be great to see a progress messages / bar during the computation :-)