Provide shorthand for list of = filters without using regular expressions

[nebulon42]

Instead of having to write e.g.

[type='motorway_link'],
[type='trunk_link'],
[type='primary_link'],
[type='secondary_link'],
[type='tertiary'],
[type='tertiary_link'],
[type='unclassified'],
[type='residential'],
[type='living_street'] {
...
}

allow writing e.g.

[type in 'motorway_link', 'trunk_link', 'primary_link', 'secondary_link',
'tertiary', 'tertiary_link', 'unclassified', 'residential', 'living_street'] {
...
}

Avoid regular expressions because of possible explosion of rules due to #213.

[pnorman]

The main use I see is when combining with another rule to reduce duplication of writing that other rule.

Most of the code I've written that looks like this add another rule add zoom, and zoom isn't constant across the different types of feature so an in construct wouldn't help there.