Shortbread boundaries

[joto]

First commit: Boundary lines in shortbread have no names

Do not add the names from boundary ways to the output. Some ways have names but use is inconsistent and generally not useful in this context.

Second commit: Fix shortbread boundary processing in regards to disputed boundaries

The way disputed boundaries are implemented was not correct. Generally boundaries should be processed as if disputed boundaries do not exists. But then all boundary lines created from ways that have the disputed flag set or that are in a relation tagged boundary=disputed will be marked as disputed.

Note that the relation that marks a way as disputed is not the same relation that marks a way as part of some specific admin boundary. The first is tagged boundary=disputed, the second is tagged boundary=administrative.

This is based on the work in #10 but rewrites the code to be (hopefully) easier to understand.

Note that this only fixes the version for shortbread_v1, the version for shortbread_v1_gen also needs updating which will come later.

[lonvia]

The disputed relation handling is still not completely correct. If a disputed relation has an admin_level tag, then you would only want to mark the boundary way as disputed if its own level is equal or higher. That means you need to save the level to which the dispute applies.

[joto]

I have changed to commit to take admin_levels of relations tagged boundary=disputed into account.

[lonvia]

Still not right, because admin_level will now be nil when object.tags.admin_level is set but is not a number. Must be: local admin_level = tonumber(object.tags.admin_level or 1) or 1

[joto]

I have added an explicit function instead which makes it more explicit what's happening here.

-- Get numerical admin level from string, default to 1 if invalid
local function get_admin_level(value)
    if not value or not string.match(value, '^[1-9][0-9]?$') then
        return 1
    end

    return tonumber(value)
end