Legacy note on top and removed other legacy projects

[lipis]

Made it more clear for the newcomers that this project is unfortunately legacy.

Also flask-boilerplate and flask-appengine-template more or less share the same destiny, as you can see it from the latest commits:

• https://github.com/mjhea0/flask-boilerplate/commits/master
• https://github.com/kamalgill/flask-appengine-template/commits/master

I added gae-init in a more prominent spot as this project is pretty much up-to-date, comes in different flavours as separete projects, with documentation and very active.

Lastly you can see that the project is being used all around the world and there is no plan to stop the support in the future :)

• https://gae-init.appspot.com/stats/
• https://gae-init.appspot.com/stats/month/