fix favicons and add an option to enable svg

packages/rocketchat-assets/server/assets.coffee

packages/rocketchat-i18n/i18n/en.i18n.json

packages/rocketchat-ui-admin/admin/admin.html

packages/rocketchat-ui-master/master/main.html

packages/rocketchat-ui-master/server/inject.js

packages/rocketchat-ui/package.js

public/images/browserconfig.xml

public/images/manifest.json