General refactor - Githubissues

This pull request is intended to full refactor and reorganize the pipeline, turning it into a python package compilant with all Python standards.

Tasks:

[x] Move python files to sub-directories
[x] Add required package files.
- [x] setupy.py
- [x] pyproject.toml
- [x] manifest.in
[x] Add a license to the code.
- [x] Update the license file to add the program informations.
- [ ] Change the license header of all files.
[ ] Move the manual to a docs subfolder using a git friendly format. May be latex? mardown?
[ ] Generate pipeline library docs.
[ ] Cleanup the code to follow PEP8 and PEP257
[ ] Add executables as script entry point. See Command Line Scripts or Console Scripts.
[ ] Move products to classes with read and write methods.
[ ] Create classes for pipeline steps. This classes will be called from actual functions using __call__ method to avoid break current workflow design.
[ ] Turn the parameters in a specialized class that have default values and explanation.
[x] Add changelog file.
[x] Update the notebooks to use the new paths.
[ ] Use astropop 1.0 API.
[ ] Remove ROOTDATADIR and ROOTREDUCEDIR from default parameters. They must be user specified.
[ ] Split pipeline_lib.py into a submodule. The file has 2500 lines!

Only turn this draft in a ready PR after all tasks are good to go.