General update of the README
General update of the README

Change all links to google photo instead of dropbox. Add information about
the Large and modular diy kit. I think we need to find a better name for
these things soon...

Signed-off-by: Robin Hagman <a0ad21b4a5c77bde0f74c8a70cf9b810eabd0434@gmail.com>

rhagman/sustainable-green-plants