Resolve "Add detector node "spectrometer""

Closes #30

See merge request !4

This is only a preliminary solution until we have a general reporting.

Copied from EnergyMeter. Needs modifications yet.

Resolve "Add detector node "Energy meter""

Closes #29

See merge request !3

Update docs. Update filter_test example.

Resolve "Add outgoing port to detector node"

Closes #21

See merge request !2

Update documentation.

Resolve "Spectrum: Add serde serializer / deserializer"

Closes #23

See merge request !1

Tiny doc fixes.

Add serde_yaml crate and add Serialize to spectrum.