adds desktop filters button and functionality

...h/apply/funds/templates/funds/base_submissions_table.html

...ech/static_src/src/javascript/apply/submission-filters.js

opentech/static_src/src/javascript/main.js

opentech/static_src/src/sass/apply/abstracts/_variables.scss

opentech/static_src/src/sass/apply/components/_button.scss

opentech/static_src/src/sass/apply/components/_filters.scss

opentech/static_src/src/sass/apply/components/_form.scss

...tech/static_src/src/sass/public/abstracts/_variables.scss