Replace styleID property with styleURL__ inspectable

[1ec5]

This PR replaces the styleID convenience property with an Interface Builder inspectable (normally inaccessible from code) that imitates a URL field. styleID is inconsistent with other GL-based APIs, and we never implemented a convenience initializer that took a styleID anyways, so it had limited usefulness as a separate property.

The new inspectable’s name is a horrible hack and is marked as such. I’ve filed <rdar://problem/23134321> against Interface Builder to request support for NSURL-typed inspectables.

I considered merely deprecating styleID but wound up cutting over in a manner similar to #1561. styleID is primarily used as an inspectable. Deprecating an inspectable leads to a horrible user experience, because the inspectable’s value continues to work even though it silently disappears from the Attributes inspector. (You’d have to know to go to the User Defined Runtime Attributes section of the Identity inspector.) If you ever tried to re-set the style, this time via the new “Style URL” inspectable, you might run into weirdness like #2626. This backwards-incompatible change requires bumping the version up to 3.0.0.

This PR also removes some APIs that have been marked unavailable for a few releases, since back before the iOS SDK left the 0.x series.

Fixes #2628.

/cc @jfirebaugh @incanus @bsudekum @friedbunny

[1ec5]

Before merging, I need to address invalid URLs by asserting.

[friedbunny]

I'm on the record as being not un-in-favor of huge version numbers. Will give this a spin tomorrow!

[friedbunny]

Looks good and works in practice. 👍

[incanus]

Question: we are considering bumping to 3.x.x for this, correct? Is there any way we can not do that (just checking)?

[1ec5]

As explained above, we could have a non-inspectable property with the old name, as a compatibility shim. However, that’s no way to deprecate a symbol: developers will never see any indication that styleID has gone away. If they even have a reason to look at MGLMapView’s inspectables, all they’ll see is that there’s a new “Style URL” field that’s blank. If they set that inspectable (since it was never their intention to use the default style), the result would be potential problems like #2626 (if the URL matches the hidden ID) or undefined behavior (if it doesn’t).

This is a unique case, and I think the set of inspectables we’ll have after landing this change will be pretty stable for awhile, modulo any Interface Builder enhancements to their inspectable support.

[tmcw]

Is this change going to be reflected in the Android SDK?

[1ec5]

The Android SDK has never had an independent styleID getter or setter: #1947 (comment).