CSS overrides and various minor UI updates

- Added vw unit overrides for various font and button elements
- Styled login / signup text links as clear buttons so that they have a
larger tap target on a all devices and for enhanced readability.
- Fixed swipe disable on welcome screen
- Fixed ionic bug that smushes elements when a slide box is rendered by
adding update method to slide box
- Force logout to reset the welcome screen active slide index to 0
- Added placeholder  to Memberships screen
- Added placeholder picture to Home screen
- Added profile and QR code icon to menu