Begin improving DSL section

Based on the notes I took while discussing
the build and the server code in Dundee.

 * Add model-generation.png from the Nature paper
 * Merged TypeLanguage into Model
 * Added specifics comments about generated files
Suggested fixes
Merge remote-tracking branch 'origin/dev_4_4' into model-generation

Conflicts:
	developers/Model.txt
	developers/Server/ExtendingOmero.txt
Add paren and command ticks, suggested by Helen

The changes are quite small but to maintain line
lengths I formatted the paragraphs.
Merge pull request #242 from joshmoore/model-generation

Begin improving DSL section