Selective update shows better error message on conflict

[mrinaldi]

When I'm updating a single package, the conflict message would not show the other packages requirements that has conflicted.

paket.dependencies:

source https://nuget.org/api/v2

nuget Ninject.Extensions.Interception
nuget Ninject.Extensions.Logging.Log4Net

paket.lock:

NUGET
  remote: https://nuget.org/api/v2
  specs:
    log4net (2.0.3)
    Ninject (2.2.1.4)
    Ninject.Extensions.Interception (2.2.1.2)
      Ninject (>= 2.2.0.0 < 2.3.0.0)
    Ninject.Extensions.Logging (2.2.0.4)
      Ninject (>= 2.2.0.0 < 2.3.0.0)
    Ninject.Extensions.Logging.Log4net (2.2.0.4)
      Ninject.Extensions.Logging (>= 2.2.0.0 < 2.3.0.0)
      log4net (>= 1.0.4)

paket update nuget Ninject.Extensions.Logging.Log4Net version 3.0.1
Outputs:

  Could not resolve package Ninject:
   - Ninject.Extensions.Logging 3.0.1 requested >= 3.0.0.0 < 3.1.0.0

This PR changes to output message to include what other packages have conflicted:

  Could not resolve package Ninject:
   - Ninject.Extensions.Interception 2.2.1.2 requested >= 2.2.0.0 < 2.3.0.0
   - Ninject.Extensions.Logging 3.0.1 requested >= 3.0.0.0 < 3.1.0.0

[forki]

Very cool. Love it