Create Project Type resource

[s-espinosa]

Currently project_type is a string that lives on the projects table. This means that for dropdown menus we pass arrays of strings to the views (e.g. in project#new). Would be better to add these as a separate resource with only an id and name.

Will need to create migrations, update methods on project, seed the new table and preserve existing data (in a migration?) prior to removing project_type from the projects table.