UI refactor

[jakozaur]

This is a giant change. Mostly move and rename with minor delete of unused code.

Principle:

• replace html_pages and html_panels with filer per each tab
• reduce the amount of exposed public API using internal and private name
• keep every non-test file below 300 lines

Long term goals:

• Make UI configurable (e.g. port, disable debug, limit amount of messages)
• Be able to refactor so one UI can attach to multiple quesma consoles
• Make modular UI, so it's easy to add new tabs, even for occasional use case

More changes will follow (e.g. more packages, configurability)

[nablaone]

I like the internal package.

LGTM