Support downloading an installer with a semantic version expression

[isc-tleavitt]

Key motivating use case:

s version="latest" s r=##class(%Net.HttpRequest).%New(),r.Server="pm.community.intersystems.com",r.SSLConfiguration="ISC.FeatureTracker.SSL.Config" d r.Get("/packages/zpm/"_version_"/installer"),$system.OBJ.LoadStream(r.HttpResponse.Data,"c")

This is right if you want to download and install the latest version. It's dead wrong for CI because the latest version might have an incompatible semantic version with what you expect.

Rather than pinning to a specific version, it would be nice if we could set version="^0.9.0" to pick up backwards-compatible changes to version 0.9.0.

If it's easy to extend this to other endpoints that would be fine too, but the IPM installer is really the most important for this (as most of the time you'll be going through the IPM client otherwise).