qsignature implementation

Hi,

I finally added qsignature. Please, take a look if I did everything correct. It is working with test data.

There are two main points that will need work:
* only for human, I think that happy with that for now

* __memory usage__, right now I am using only chr22 for the analysis to make sure we just use 8Gb (as well there is a downsample in case chr22 is giant). I will work to implement a better way to calculate the expected memory, to allow the analysis of an entire genome. 

* __report__ : there is a matrix file with the score distance between samples, so you can inspect this doing a heatmap, and a warning that is inside project.yaml in case the score is <0.1, seems a good score for duplicated samples. 

I created a function inside `qcsummary.py`: `_sclice_chr22` (to get only chr22), but don't know if it would be better to be inside `bam/__init__.py`

any feedback welcome. 

thanks