Proposed changes to state passed to plugin journal_entry().

[Athanasius]

Heads up to Plugin Developers - Please take a look at this PR #1206 as we really want to make the core monitor code (which provides the state that's passed to plugin journal_entry()) more robust against typos and brainfarts.

This PR is looking at using a custom dict type to set specific types on the members to catch at least where we brainfart a wrong-type value. That checking would be when using mypy, not runtime.

Another issue is that using a simple dictionary for that state means nothing will catch if we typo e.g. ShipIdent as ShipIDent. There's another not-PR, but WIP, which will actually change all of state to an actual object with properties instead of dictionary member names, but with some backwards compatibility.

Mostly right now I'd like to know if any plugin developer knows their code does checks like if state['something'] is not None or the like which will trip up if we change our "not yet set"/default value to '' for strings, 0 for integers, {} for dictionaries and the like.