Validation zhuzh-up: link attribute value checks

[KasiaKoz]

Resolves #19 - Check for infinite values
Resolves #82 - Check for negative values

As a bonus this PR also adds checks for fractional values and re-organises the functions that provide the conditions for the checks - it was starting to get very crowded in the validation method.

Fixed a bug I didn't know existed - the method was not testing nested values for additional attributes, it's good that I caught that now that we're using them more!

It also improves the logging of any issues with the network, e.g.:

2022-08-25 16:32:52,084 - Checking validity of the Network
2022-08-25 16:32:52,084 - Checking validity of the Network graph
2022-08-25 16:32:52,084 - Defaulting to checking graph connectivity for modes: ['car', 'walk', 'bike']. You can change this by passing a `modes` param
2022-08-25 16:32:52,084 - Checking network connectivity for mode: car
2022-08-25 16:32:52,084 - The graph for mode: car has: 3 connected components, 1 sinks/dead_ends and 1 sources/unreachable nodes.
2022-08-25 16:32:52,084 - The graph has more than one connected component for mode car! If this is not expected, consider using the `connect_components` method to connect the components, or `retain_n_connected_subgraphs` with `n=1` to extract the largest component
2022-08-25 16:32:52,084 - Checking network connectivity for mode: walk
2022-08-25 16:32:52,084 - The graph for mode: walk has: 0 connected components, 0 sinks/dead_ends and 0 sources/unreachable nodes.
2022-08-25 16:32:52,084 - Checking network connectivity for mode: bike
2022-08-25 16:32:52,084 - The graph for mode: bike has: 0 connected components, 0 sinks/dead_ends and 0 sources/unreachable nodes.
2022-08-25 16:32:52,085 - Checking link values for `length`
2022-08-25 16:32:52,085 - 1 of links have zero values for `length`
2022-08-25 16:32:52,085 - 1 of links have fractional values for `length`
2022-08-25 16:32:52,085 - Checking link values for `capacity`
2022-08-25 16:32:52,085 - 1 of links have negative values for `capacity`
2022-08-25 16:32:52,085 - 1 of links have infinite values for `capacity`
2022-08-25 16:32:52,085 - Checking link values for `freespeed`
2022-08-25 16:32:52,085 - 1 of links have zero values for `freespeed`
2022-08-25 16:32:52,085 - 2 of links have negative values for `freespeed`
2022-08-25 16:32:52,086 - Checking link values for `modes`
2022-08-25 16:32:52,086 - Checking link values for `{'attributes': {'osm:way:id': 'text'}}`
2022-08-25 16:32:52,086 - 1 of links have zero values for `{'attributes': {'osm:way:id': 'text'}}`

Compared to:

2022-08-25 16:32:15,334 - Checking validity of the Network
2022-08-25 16:32:15,335 - Checking validity of the Network graph
2022-08-25 16:32:15,335 - Checking network connectivity for mode: car
2022-08-25 16:32:15,336 - Checking network connectivity for mode: walk
2022-08-25 16:32:15,336 - Checking network connectivity for mode: bike
2022-08-25 16:32:15,337 - 1 of links have values of 0 for `length`
2022-08-25 16:32:15,337 - 1 of links have values of 0 for `freespeed`
2022-08-25 16:32:15,337 - 1 of links have values of 0 for `id`

before.

Nb. More PRs in the validation theme coming up soon. I'm leaving updating the notebook: 6.1. Validating Network: MATSim Specific to last in the series.

[mfitz]

I've added a few minor comments - should be small changes if you agree with them.

[KasiaKoz]

Some minor updates plus:

• added dataclasses to represent conditions for testing network link attributes
• added one more condition checking for None values