Replace "firstRun" config option with "openSidebar" and "openLoginForm"

[nickstenning]

This commit deprecates the confusingly-named "firstRun" embed script option with two which actually describe the relevant actions triggered.

Unfortunately, at the moment this requires a fairly horrific check that the string value of a config option is not the literal 'false', due to the way that the Host code passes configuration from the page frame to the sidebar frame (using URL query string parameters).

To make up for that, I've added a docs/config.md file in which to document these configuration options.

[nickstenning]

See also hypothesis/h#3643, which should be merged and deployed before this.

[nickstenning]

We should probably also actually detect the firstRun option in use (for embeds, for example) and emit a console deprecation warning.

[seanh]

LGTM. @chdorner any reason not to merge this now?

[chdorner]

@seanh should be good to go now, I just released the corresponding change in h to production (which sets old and new configuration settings)

[robertknight]

Unfortunately, at the moment this requires a fairly horrific check that the string value of a config
option is not the literal 'false', due to the way that the Host code passes configuration from the page
frame to the sidebar frame (using URL query string parameters).

Possible dumb but simple solution:

host.coffee:
  options.app += '?config=' + btoa(JSON.stringify(appOpts))

app.js:
  settings.config = JSON.parse(atob(queryString.parse(window.location.search).config));
  // change references to settings.<configOpt> to settings.config.<configOpt>

[robertknight]

LGTM. I'll merge this and post a potential simplification as a follow-up