PUP-2745 Forge malformed dependency fix

Prior to this commit a malformed name in the dependencies for a downloaded forge
module dependency would cause the PMT to fail unexpectedly.
This commit causes the PMT to ignore malformed dependencies.

Depends on https://github.com/puppetlabs/puppet/pull/2827
`@full_module_name` is equivalent to `@username` and `@name`.  `@repository` is ignored by, well, everything.

What we actually care about is `@full_module_name` and `@version_requirement`.