publish prerelease to pypi

What do these changes do?

Publish all commits on master branch of the main repo to Pypi.
Don't publish to testpypi (no need anymore as dev/stable releases are distinguished directly by versioning)
Once this goes in users can install the stable version of osparc by running pip install osparc and the latest dev version (prerelease) of osparc by running pip install osparc --pre. In short, there is no longer a need for users to access testpypi to get the latest "dev" version of osparc client