Readability / beautification work

[sethtroisi]

• Drop 19x19 in model names.
• Add help icon / readme in Header bar
• Add "Zero to MG in five minutes" guide (colab for converting weights?)
• links to weigths from cloudy (https://cloudygo.com/converted_model/v16-19x19/models/)

[sethtroisi]

• Add / update a hello world page on Cloudygo
• Link to CloudyGo from Minigo project

[sethtroisi]

• more prominent name and size in header bar
• blocks/filters in model page
• download / link in model page

[alreadydone]

Conversion script on Colab (courtesy of @godmoves)
https://colab.research.google.com/drive/16eXKg_WswzadfpfbIZzATcSy0qL7F0gC

[alreadydone]

Someone also made a convert_minigo.exe (supposedly using PyInstaller) which is 34.6MB in size but saves python and tensorflow installation, so an overall gain!