Trigger events on sidebar open/close

Useful for logging/reactive code.
[chrome] Factor out sidebarfollow code.
[chrome] openOrFocus is really toggleOrFocus.
[chrome] Don't set the default popup

Fixes #73
[chrome] Fix manifest line-endings.
Give install notes consistent IDs

Also, don't mark them as modified. This ensures that they will be
deleted on sync if they were deleted on another computer.
Add option to hide formatting buttons

closes #168