fix problem du to new pysam api
- fix requirements
adopt more pythonic architecture
- scripts are in lib subdirectory, with a console_entry in setup
- tests are not anymore in nested treefile, test can be run from setup
- update copyright
- documentation
- use 2 files to set requirements and reqirements for developers

some images have some sghtdiifrence with the reference
due some rounding value when use log on so on
so I compute a basic distnce between 2 images and allow a delta

a normalization was always applied linear or log  on whole matrix or by
row. but linear on whole matrix was the default and apply when option
was ommited.
to be more transparent add value 'lin' in accepted values for --norm.
'lin' is the default so now the normalization is more explicit.
but the behavior is the same.

fix the name of normalisation function ccording new option values
fix unit test according new function names
fix documentation according new api