Smartdown version of register a birth

**Smartdown version of register-a-birth**

This work corresponds to the epic: https://www.agileplannerapp.com/boards/105200/cards/7983

**What does this contain?**

1. Write all the Smartdown for register-a-birth (including plugins)
2. Write all the utilities and rake tasks necessary to prove that transition in complete (in particular, comparison tasks)
3. Move scenarios to rake tasks so that they can be:
  - run independently for an individual Smartdown flow
  - stop breaking the build... use of global $imminence and $worldwide_api variables was making dynamically generated tests such as scenarios break horribly: for more details on the horror, come talk to me :)
4. Documentation on new rake tasks

If you want to take a look at the outcomes of the various rake tasks, please see:
https://github.com/camilleldn/smart-answers-metadata

**Future work**

Fix two bugs in Smartdown linked to the odd gsub behaviour in compare helper that is removed in the penultimate commit of this pull request
The two stories to fix them are:
- https://www.agileplannerapp.com/boards/105200/cards/9008
- https://www.agileplannerapp.com/boards/105200/cards/9009

**Still to do**

* run scenarios as part of test task
* final comparison run once phase 4 changes have been put in place (cc @jackscotti)
* determine what needs to happen with metadata created by those rake tasks and how they can be used to create a more robust "diffing" system for testing (cc @dsingleton )
This might cause some conflicts due to the fact that I'm working on Register a Birth. Let's keep it in mind when we will merge my next PR.