Relationship resolver now uses KSP version in resolution.

`LatestAvailableWithProvides` now requires a mandatory KSP version, so
we don't accidentally do this again.
CKAN.dll: LatestAvailable now requires a version number

This means we can never go looking up mods which may be the wrong
version for our install by accident. It may also fix some edge cases
like #602 where we may show the wrong versions being available.

Most of the changes in this commit are to the test cases, which now
require the mandatory argument. :)

Tested that this closes #610 with our NEAR test example.
Merge pull request #611 from pjf/610_relationship_resolver

Bugfix: Always use current KSP version when resolving relationships