Support live/preview/paused mode for logging in to sites without capturing login info

[ikreymer]

We've had this in webrecorder.io originally but removed it as it didn't work for hosted service, but works quite well locally. The idea, similar to Browsertrix profiles, is that a user can 'prepare' the browser by logging in to whatever sites they'd like without recording anything. When they're all logged in, they switch to recording. It should probably be another mode, only available in the app, not sure what best term for it is. Workflow might be like this:

• From landing page user has option to 'Start' or 'Prepare Browser'
• If 'Prepare Browser', they're taken to the live browsing mode (mode selector says Preparing/Not Recording)
• User can log in to as many sites as they'd like
• User can press stop, which would return to landing page, or switch modes to Capture (which would reload the page fully, but with user already logged in)
• The account settings page can have a 'Clear Cache' button that will clear the cache on the browser/reset all logins. (In the future, could even support multiple profiles but probably not needed for now)

[ikreymer]

Implemented via cookie prepare feature!