add overlay to download modal
move styling to downloads css file and add overlay styling
style the download modal
Merge branch 'master' into style-download-modal

Conflicts:
	app/assets/javascripts/protected_areas.js.coffee
refactoring for better initialisation of modal and map
add downloads css to application require statements
remove unneded vendor prefixes in css
normalize font weights in downloads.css.scss
Merge pull request #35 from unepwcmc/style-download-modal

Style download modal