Feature/logging

[phatsk]

Name says it all - this PR provides a logging interface in the UI.

• Display window for logging when a Sync starts
• Process flat arrays of log messages
• Support for all object types
• Paging/reducing log size every n lines
• Ability to hide/show log window in UI
• Unified logging mechanism in code

[phatsk]

Basic logging of all object types should now be ready. Log lines are prefix with identifiers, currently they are:

• [i] for informational lines
• [d] for debugging lines
• [e] for error lines

Eventually, we can parse these to display more "pleasant" logs in the interface, rather than just a <textarea>. I'm thinking we can have a table and use these identifiers to style the rows appropriately, as well as add filtering at some point.

I've removed the ability to hide the Log window from the "roadmap" for this feature for now - the log will only appear once a sync begins, and I think the information is relevant enough to keep it displayed. We can revisit that later if we need to.

I haven't added the ability to "clean" or page the log yet, not sure if that's still something I want to do. I'd like to see how hefty the log view gets for Very Large Websites before figuring out if that's something we need to consider.

All-in-all, I think this is ready for an initial review.