Add Documenation about classes

[Kaligule]

Going through the code I notice that the classnames were choosen to contain meaning, but this is not documented and they are not as selfexplanatory as the author might have thought. Examples are:

• Bot (What is a bot?)
• Update (Is this an update of a single package or of all packages in the repo? What is the difference between InitialUpdate, SequentialUpdate, ScheduledUpdate and BundledUpdate?)
• Config (What is configured? A Bot? A PR? Everything?)
• RequirementsBundle (I have no idea what this might be.)

It would be cool if these classes would have docstrings that describe their scope. This would greatly improove the experience for new potential contributors.