Add step progress model
Add step_progresses to users
Add project progress model
Annotate models
Create introduction_step_progress
Add project user progress methods
Add introduction step progress and many methods for callbacks to update the project progress
Add blank specs for introduction step progresses
Annotate the introduction step progress model
Track starting steps
Add methods for starting a completing an introduction_step
Add methods for starting and completing a step
Method for projects to see all steps
Fill in bodies of step progress and introduction step progress
Fix merge in schema