Allow links to have a time delay for chained run-of-river plants

[nworbmot]

Allow links to extract energy from a bus in one hour, and feed it into another bus in another hour. This would allow to represent, for example, a river connecting two run-of-river plants, where the water takes a non-trivial amount of time to flow from one plant to the other. Introduce an integer attribute "delay" to the Link component which specifies how many snapshots ahead/behind the energy supply to bus1 is. Also need a boolean attribute "cyclic" to specify what to do with the energy at the start and end of the period under consideration.

[fneum]

This could also be interesting for gas networks (in a transport model via links) to model time delay.

[euronion]

And for shipping.