settings for dependent packages should be respected - #919

Consider a paket.dependencies file:

source api.nuget.org/etc/etc

nuget A
nuget B content: none

and a paket.references file in a project that just specifies a dependency on A

Now imagine that B is a dependency of A

Right now on install for a project we take the full set of packages [A,B] and extract from it the top-level dependencies of the project, resulting in [A]. We then configure the installSettings for this dependency, which in this case is the empty InstallSettings.

After we build the top-level map we augment it with the n-tier dependencies of each top-level dependency, and use the parent's configured InstallSettings only. This results in an install of package B where the content: none directive is not honored.

This pull request resolves the settings for the n-tier dependencies in a similar manner to the top-level dependencies, while allowing any top-level dependency settings to override the settings configured for the lower-level package if any are present.