Add updateinfo xml generator.
README: add instructions for writing release notes.
Fix README markdown.
Merge branch 'master' into gen-update-xml

Conflicts:
	_config.yml
UpdateInfoGenerator: extract download links to _config.yml.
Add description in README.
Fix update info generator: download page should be full url.
Merge branch 'master' into gen-update-xml
Merge branch 'gen-update-xml'
Rename latest-version.xml to latest.xml