Only add the public principal to the annotation

We now wait until the annotation has been created and apply the
principal to the read array rather than overwriting the entire object.
Merge pull request #1585 from hypothesis/fix-replies

Only add the public principal to the annotation
Add tests for updated reply behaviour
Remove all assets for the help documentation
Move masthead image styles under masthead namespace
Add some styles for the onboarding/help page
Add initial content for the help page
Reduce the amount of content on the help page
First run through of the onboarding/help page
Show help/dev sections based on rendered page
Add new onboarding page under /welcome
hypothesisConfig now extends the default options

This saves the implementor redefining the defaults if they only want
to override one or two options.
Add firstRun flag to the hypothesisConfig in help
WIP Show the sidebar on load

If the firstRun option is provided to the hypothesisConfig.
Add move icon to the font set
Add onboarding specific intro to help page
Add link to the roadmap in the onboarding
Use refer to icon in the location bar on help page
Remove the Key Features section from help

Replace this with a section on privacy which is really the only
important point in there and shuffle the sections around.
Improve the responsiveness of the onboarding page