Write missing pages in documentation

[markgw]

There are lots of TODOs in the docs.

See list in the docs.

All of these should be filled in before v1.0 release.

Current TODOs that need to be addressed are the following

• [ ] More detail on module dependencies
• [ ] Examples of module dependencies
• [ ] Code structure for modules
• [x] Pipeline variants
• [ ] Guide to building map modules
• [ ] Use different (public) dataset in tutorial
• [ ] Dependency feature extractor for embeddings
• [ ] Key-value to term convertor
• [ ] Term-feature matrix builder
• [ ] Term-feature vocab builder
• [ ] Term-feature vocab mapper
• [ ] Malt module
• [ ] OpenNLP coref
• [ ] OpenNLP parser
• [ ] Regex matcher
• [ ] Any others in this list added since I wrote this.