Replace existing and add additional Favicons

[sebrock]

Favicons required in /src/assets/favicon in different sizes and formats for a number of platforms.

Analysis of existing favicons brought to light some deficiencies:

Replace the with Banano icon accordingly.

• android-chrome-192x192.png
• android-chrome-512x512.png
• apple-touch-icon.png (180x180)
• favicon.ico
• favicon-16x16.png
• favicon-32x32.png
• mstile-150x150.png (Windows 8 / IE11)

and

• Add all missing ones to provide support for as many platforms/browsers as possible

[sebrock]

Corrected <link> and <meta> tags relevant to favicons in /src/index.html starting line 29
Remember to adapt for final app/site name (added to Issue)