fix lists with paragraph text; put text in quotes when necessary

- clean superfluous nodes from AST
- don't add endline before paragraph if paragraph is primary list item text
- quote alt text if it contains a comma
- quote link text if it contains a comma
- handle linked images in a cleaner way
ignore eclipse project files
resolves #12 only add source style if language is specified
resolves #14 add implicit links and cross references

- drop label from link if it matches URI
- use cross reference syntax for internal links
revise description lists

- rename from definition lists to description lists
- drop glossary style
- correct indentation of term
Renamed definition lists to description lists
Merge fix