Global: Light Mode Style Updates

[luke-freeman]

Update the light mode version of the app to match the website.

• Remove all instances of the grey background
• Add drop shadow to cards and search box
• Adjust drop shadow of the bottom navigation

It should look similar to this:

You can find full designs for light mode here

https://www.figma.com/file/LCwFKA0AmG9EcOQPBamGAb/Emitron-iOS?node-id=0%3A2533