Prepare for Pip package management

[alexander-bauer]

This PR restructures the repository to allow it to be packaged easily by Pip. Metadata and dependencies are listed in setup.py, and easyucs can be installed from this repository via a normal Pip invocation.

Former scripts easyucs.py and easyucs_gui.py are turned into Python modules (that are members of this package), and replaced by convenience scripts easyucs and easyucs_gui that simply invoke those named Python modules.

Documentation is adjusted to refer to the new convenience scripts. Some formatting is added, and some trailing whitespace is removed.

A .gitignore is added to ignore files and directories left by Pip and virtual environments.

Much of what this PR addresses is mentioned in issue #2.