Start major refactoring of recurring_todos. Started with creating new recurring todos. 
All current and new tests pass
remove unused code and refactor builder to remove duplication
use new model to handle updating of recurring todos
small cleanups
move mapping of form attributes to model attributes from pattern to builder to make
pattern independent of form
move model validation into pattern classes and link from recurring_todo model
make validations a bit more dry
move form specific accessors out of model