Add Basic Issue collection.

1. Issue Model is created in app.py
2. Project issues are created and saved in run_update.py for each project
Add basic /issues endpoint
Add basic issue/project relationship. Database foreign keys are missing
Add issues to /projects endpoint
Update tests to have /issues endpoint
Add Issues to index.html
Update run_update.py to mark and delete issues using 'keep' entry in DB.
Made project/issue relationship
Update: run_update.py saves issues with corresponding project.id
Add cascade delete effect from Project to Issues