Multiple Remotes with different sources does not lead to error

[wes-a2ai]

Feature

rv provides a way to override explicit version and ignore other installation guidance such as remotes present in description files

Use case

Override conflicting installation requirements embedded in different packages to make a full resolution graph that is solveable

Out of scope

Determination if the overriding version may cause runtime conflicts

Implementation detail

the override should still respect package version constraints when solving the graph - eg if a package says pkgA >= 1.0 and we attempt to override with pkgA 0.8 it would produce an unsolveable graph, so this would be in scope for overriding different remotes/config needs/etc instructions

[Keats]

I believe #208 will fix that as well? I need to add a test for that