add BTSTACK_EVENT_POWERON_FAILED description

git-svn-id: http://btstack.googlecode.com/svn/trunk@2818 1a0a8af8-31b5-11de-8e0c-53a27eea117e
generate.py moved to tools

git-svn-id: http://btstack.googlecode.com/svn/trunk@2819 1a0a8af8-31b5-11de-8e0c-53a27eea117e