add unsaved changes warning to funding stream

[smcalilly]

from documentation comment:

we should probably stay consistent about warning the user of unsaved changes before they leave the page. this doesn't happen on the main branch for fundings atm

[jim-z]

Edits to existing project overview page details are automatically saved without me having to click "save project". Phase page details are not. Should either make auto-save consistent across the platform or add warning about changes not being saved when user tries to navigate away from page.