Sensible defaults for searching for beliefs (e.g. most recent beliefs)

[Flix6x]

most_recent_beliefs_only=True seems like a sensible default for Sensor.search_beliefs. I'd propose to keep most_recent_beliefs_only=False for TimedBelief.search.

(Inspired by discussion in #307.)

[nhoening]

Why do you propose to use False in TimedBelief.search?

[Flix6x]

I like our starting point (from timely beliefs) in that the defaults for all search parameters have the same connotation: "If you don't set any, you get everything". Here we're discussing to deviate from that logic to: "If you don't set any, you get the most recent beliefs about all events". I guess there's something to be said for keeping the defaults of both (FlexMeasures) functions in sync.

[nhoening]

I found this comment difficult to translate into what actions you propose on FM and TB levels.

[Flix6x]

I propose to change the defaults for FlexMeasures only, and keep timely-beliefs as is.