More detailed explanation of the two variants of using time.

[HansOlsson]

Closes #3855

[henrikt-ma]

I get the impression that it should be emphasized that it can be part of a discrete-time sub-partition?

Suggested change

	The most intuitive is \lstinline!sample(time)! which works in any clocked partition, similarly as sampling any other continuous-time variable.
	The most intuitive is \lstinline!sample(time)!, which can be part of both discrete-time and discretized sub-partitions, similarly as sampling any other continuous-time variable.

[henrikt-ma]

Instead of all these one or two sentence paragraphs, I think it will look better if we merge everything into a single non-normative paragraph on the theme of time.

Suggested change

[henrikt-ma]

As above:

Suggested change

[henrikt-ma]

I didn't see the value of saying without any restrictions. Would this simplified one-sentence alternative work?

Suggested change

	Additionally, \lstinline!time! can also be directly used in different clocked partitions without any restrictions.
	However, every sub-partition directly referencing \lstinline!time! contains a call to \lstinline!der!, which makes it a discretized sub-partition \cref{discretized-partition}.
	On the other hand, if \lstinline!time! is used without sampling it in a clocked partition, it brings a use of \lstinline!der! to its sub-partition, and hence the sub-partition must be a discretized one (compare \cref{discretized-partition}).