Feature/ems csv prediction

[josellausas]

About

• Adds support for ems column to import-predictions command
• Adds EMS Prediction to Department detail template
• Adds ems to the model and generated migrations
• Fixes issue when strings are mixed with numbers in prediction CSV.

Relevant Issues

• Closes Update predictions loading process to include EMS #515

Testing Instructions

1. Run ./manage.py import-predictions scripts/ems.csv
2. Go to a department with EMS prediction data (http://192.168.33.15:8000/departments/87255/los-angeles-county-fire-department) and check if prediction is shown