Remove upper bound for tile imagery resolution.

[kyonifer]

Description of the Change

On the current develop branch, worldwind limits the resolution of image tiles to 0.5m. When visualizing scenes which are low to the ground (such as geolocated vehicles) this can be insufficient resolution to view a scene in full detail.

This PR removes the artificial limit in mustSubdivide, which in turn allows the layer providers to regain control over the maximum resolution they can support. For example, the Bing tiled image layer supports 23 levels of imagery, some of which are unavailable before this MR because mustSubdivide begins returning false before the higher levels are reached. A side-by-side comparison of using the BingAerialLayer before and after this MR is below:

Current develop branch	This PR

Why Should This Be In Core?

The current resolution limit is hard-coded in core, thus must be modified there.

Benefits

The ability to render arbitrarily small scenes, which would commonly include situations such as geolocated vehicles and 3D renders of individual buildings.

Potential Drawbacks

The current limit may be there to reduce accidental bandwidth usage. In this case I'd request that a configurable option be included to set the minimum tile resolution to something other than 0.5.

[pdavidc]

@kyonifer Thank you for the precise and thoughtful contribution. At the moment, we're unable to accept external pull requests, and we're working to resolve that. We'll leave this pull request open and will address it soon.