funding and phase improvements

[smcalilly]

Overview

Fixes funding and phase-related issues from user feedback tasks:

• removes the "obligated_completion_date" field
• renames "obligated_year" to "year
• adds a range of years via a ChoiceField in the funding stream and phase forms
• changes the choices for Phase.status

Demo

Notes

For the year validation, I followed this stackoverflow example. I started to follow another answer in that thread, using the MaxValueValidator/MaxValueValidator on the model fields, but that hardcodes the year range into the migrations. By doing calculating it on the form like this PR's approach, the range is more dynamic as the years go by.

Testing Instructions

• visit review app: https://ccfp-asset-d-feature-fu-zsiaey.herokuapp.com
• login with ccfp-asset-dashboard test user credentials
• add/edit funding
• make sure the data changes show up in the phase funding table