Markdown-like package and module documentation

[uliska]

Each package and each module directory should have a README.md file (as that's what is e.g. automatically displayed on Github). These should be used as the general package/module description/documentation.

To be discussed is whether this needs some specific form or has a special range of formatting options. This has to be discussed in the context of which kind of tool we'll use to process the Markdown files. It should be very strongly recommended to use or build upon an existing tool like Pandoc, Gitbook or other Markdown-based site builders.

A specific question is whether these pages should include code examples with images. I see two options here:

• enable code examples and provide a way to automatically compile the score snippets
• provide a special link type to usage example files (see "usage-examples" style documentation #23 )

Blocks #26