Update to using template-params.xml for README.md generation.

1. Use the new process as outlined in b/18427118 to use new build
process to generate the README.md.
2. Change the icons so we have bigger icons for the web.
3. Also update the icons using icongenerator to provide all necessary
formats.

Bug: 18427473
Bug: 18427118
Change-Id: I862d8dc21ab3579c21d3597828fb61a51b6cc571
6 files changed