Make a package of the project

[fredricj]

Create a package that can be installed.
Questions:

• Naming of the package?
• hpacellseg was moved into hpacellsegmentator, does it need to be a subpackage?
• There is now version in hpacellsegmentator and hpacellsegmentator.hpacellseg which is confusing
• Can we move pytorch_zoo into hpacellsegmentator without breaking the models?

Additionally I haven't updated the README.md for the new scripts