Improve consolidation features of NuGet client

[xavierdecoster]

Scenario 1: Consolidate Lowest

Given a solution with two projects: A and B,
  And project A has package X installed, version 1.5

When installing package Y into project B
  And package Y depends on package X v1 – v2
  And expressing a *Consolidate Lowest* option (however we want to expose/implement this)

Then NuGet client should install package X version 1.5 into project B (instead of defaulting to v1 for package X)

Scenario 2: Consolidate Highest

Given a solution with three projects: A, B and C,
  And project A has package X installed, version 1.5
  And project B has package X installed, version 1.7

When installing package Y into project C
  And package Y depends on package X v1 – v2
  And expressing a *Consolidate Highest* option (however we want to expose/implement this)

Then NuGet client should install package X version 1.7 into project C (instead of defaulting to v1) 
  And attempt to upgrade package X to version 1.7 (from version 1.5) in project A.

[RichiCoder1]

👍

[xavierdecoster]

Related #1626