Add extra documentation to each package class

[pombredanne]

We should add extra documentation to each package class, possibly structured as attributes in order to better capture the breadth and depth of the data we collect to generate a summary table for all the things we have.
This could include new things:

• logos
• if a data file is a lock file or not
• extra support and capabilities in other tools like binary analysis, inspectors such as dependency-inspector
• core command(s) to generate lock file or install packages in dependency-inspector
• pointer to the main package management tool repo
• typical files extensions included (.py in pypi, and so on)
• extra documentation
• etc.

Beyond mere documentation, some of these attributes may have a practical use (like the command for dependency-inspector)

We should also track the relationship to other data files and manifests (important so we cant start treating these as pairs or groups). This could be an attribute, or a new class of its own that groups many datafile handler classes.