(2) Generic projects

Adds GenericProject instantiation of "Abstract" Project.

• Extracted presentation_location, presented_at and requires_nda to GenericProject.
• Add correct up and down migrations
• Add generic_projects scope, to narrow search to just generic projects.

Adds ActableHelper which performs route indirections. For example, project_path(@project) where @project is a GenericProject will point to generic_project_path(@project.specific). This helper is included in controllers as well to support normal project paths. It can be used to define general behavior which should work for all types of projects.

Routes under project (projects/groups and projects/roles) are moved under abstract_project (/absproject/) and are updated accordingly.

TODO:

• Fix tests and fixtures
• Verify if seeding still works
• Fix admin routes like non-admin routes
• Update en.yml with section for generic_projects.
• Test and fix db seeding