minor donation improvements & changes

donate/migrations/0040_alter_donatehomepage_lead_body.py

...e/migrations/0041_donateprojectpage_is_sticky_and_more.py

donate/models.py

donate/static/donate/assets/css/icons.css

donate/static/donate/assets/css/style.css

donate/templates/donate/base.html

donate/templates/donate/donate_home_page.html

donate/templates/donate/donate_project_page.html

donate/templates/donate/donate_project_page_coalition.html

donate/templates/donate/project_snippet.html